"A practical man can always make what he wants to do look like a noble sacrifice of personal inclinations to the welfare of the community. I've decided that I've got to be practical myself, and that's one of the rules. How about breakfast?" The Pirates of Ersatz, Murray Leinster

From your question I noticed a few things. Nominally, I completely agree with @mxyzplk's answer, so this should be in the way of an addendum.

It sucks to be the leader

In a RPG, it just completely sucks to be the leader. Most players when confronted with a plan, remember about fifteen percent of it for the first fifteen minutes. But they'll certainly remember when you deviate. Leaders get no additional responsibility and no perquisites, but they get all the blame.

In the military this is mitigated with the clear distinction between commissioned and non-commissioned officers. Not least because the isolation provides both support structures and necessary emotional distance (to a degree, of course). Being "elected" leader, especially with the pack dynamics of typical werewolf games is an extremely dubious honour that I'd flatly reject.

The fact that while you may be leader in character but not dominant over the player group makes things even stickier. You need to assert authority within the realm of the narrative without actually having that authority in reality. Again, something that will cause friction and resentment any way you cut it.

Depressing environments bleed emotions into play

The world of darkness does what it says on the tin. Having played in a horror game myself recently, the iconic themes of the world of darkness do not make for "happy" or, for that matter, validating game experiences in the main. (And, if they do, it's a violation of genre.) When you are faced with the stresses of being "leader" which are compounded by the stressors of the philosophies baked into the setting, no wonder you're having a rough time.

Some solutions:

On leadership:

Fundamentally, a gaming group is a relationship. Bad relationships that do not provide validation are a drain on mental and emotional resources. When they don't work, cut them off or change them. In your case, I'd play a game that's a bit lighter in tone and focus: a nice traditional dungeon crawl or similar heroic fantasy.

I'd also reject the leader role for all the reasons I outlined above. Or, if they force it upon you, demand the perquisites and authority that is concomitant with it: they can't have it both ways.

On the group:

I've found that group character creation creates a far more cohesive group. By having entangled backstories, the group can draw upon a deeper understanding of each others' characters, creating the basis for empathy and respect within the characters, instead of the necessary simulacrum imposed by players.

By articulating desired tropes, a "palette" (as Microscope) calls it, before the game begins, you'll be able to shape the narrative of the group in directions that you want to play. This allows you to avoid the nominally depressive tropes that come default with the setting (not limited to world of darkness) and describe a source for future characters to connect with the current group. Replacement characters, if they tie into the shared narrative, will continue to maintain the tropes and social trust.

Be practical:

As players, we shape our narratives to an amazing degree. Emulate Bron Hoddan in the Pirates of Ersatz. While playing, you will be aware of the desired practical outcome that will provide validation and satisfy your personal goals. With that outcome in mind, you then frame it in terms that suit both your character's narrative and the expected narratives of the other players such that they will act to reinforce your framing and thereby your outcome. If you fight their narrative control by "being a loner," it is difficult to achieve your own goals. If you help them work as a team and appear to sacrifice nobly on their behalf while executing your own goals... the entire process is smoother and more effective.

Note that I am not saying to lie. Instead, consider the causal constructions of your actions, the explanations for those actions to be an aspect of the role * separate* from the actions themselves. By manipulating the framing as well as the actions, you can provide the necessary hooks for the other players to support your version of reality, rather than rejecting it and, by extension, you.

Postscript

Looking at your comments to other questions, you should absolutely give this group two last tries. In the first trial (of one or two games), try a heroic romp where you can be "Big Damn Heroes." Require the players who need the spotlight be leader. In the second trial (again of one or two games), try a game where players can intrigue against each other (I'd recommend Ars Magica, but then again I recommend it for most things. Most games support PvP intrigue quite ably.) If neither game provides the validation you need and the spotlight the other players need, move on. Before you do anything, take a month break, sit down, relax, and try to game with some strangers. I'm pretty sure that if you go looking for games in the chat section of this site... someone will oblige. For more on the framing problem, I'd quite recommend Rule 34 by Stross, as it describes it in a delicious narrative context.

These are all interpersonal problems rather than gaming ones. Here's how I'd handle each of them.

Same Character I'd tolerate it. Not a big fan of this kind of behavior, but it happens. I think it's a roleplaying maturity thing.

One thing I used last game might help you. I like the list of 100 questions about your character, but didn't want to overwhelm my players with homework. Instead of asking them to fill out the list I asked them all 1 question from it before each game. This worked great because it helped grow their characters as the game progressed and because it was one question at a time they actually put thought into the answers.

I bring this up because some of the questions were useful tools to differentiate the player from the character. Asking them what advice the player would give the character, how the player and character would disagree, etc, was useful for the players who were a little too close to their characters. You could ask everyone this like I did or even ask her alone.

Setting inappropriate powers I'd brainstorm with her. "No, you can't play a robot because they don't exist in the Forgotten Realms. How would you feel about a golem?"

I think the important thing here is to work with her rather than restrict her. The idea isn't to keep her from playing a robot. It's to figure out what she is trying to express by playing a robot and then figure out a setting appropriate way to express the same thing.

Since you are the party who knows the most about both the restrictions and features of a campaign setting, you're in a better position to figure out alternatives to her ideas than she is.

I also find it helpful to use book and movie examples as a good way to communicate the feel of the game you're going for. I was trying to run a gritty and dark campaign, but one of my players wrote a 5 page faery tale for her background. With her permission I altered it, but it was clear that she wanted to play a G/PG character in my R rated game. Neither of us were happy.

Since then I've told my players what books or movies inspired the game I'm planning on running. This doesn't have a perfect success rate, because some players won't read books, but it's drastically cut down the number of mismatched characters I received. If only the Game of Thrones TV show came out before I ran my GoT game, the players might not have tried to act like an adventuring party.

Finally, it is possible that a character can't be fulfilled in a certain setting or even a certain campaign. As GM you need to recognize when this is the case. In this case I'd suggest having the player shelve that character until the next game.

Multitasking Intolerable. It's one thing if she's off screen for a while, but if she's playing she should play. If she doesn't have time for the game or if she isn't interested enough to play 100% of the time, she shouldn't be there.

This is one case where I wouldn't go for the one on one conversation. It would seem like you're bullying her. I'd lay down the law in front of everyone so that it's obvious the same rules apply to everyone.

For how to approach the situation, I think it depends on what kind of multitasking the player is doing. I'm willing to be less than polite to someone who is playing video games at my table. For homework, I'd ask nicely. Homework is an obligation, video games aren't. I'd also offer that the player could skip the game session.

Sometimes players feel like game sessions are an obligation too. I had one player with anxiety issues who was getting stressed out about game, but didn't want to miss hanging out with people. The answer for him was to invite him to come hang out while we game, but have no character of his own. I let him play NPCs when he was up for it. If your player is stressed to attend session and finish homework, try telling her she can stay at the table but not play while she's doing her homework and then when she finishes she can come back in. Tell her that it's not that you don't trust her to handle both, but that it's distracting for everyone else.

Also, to clarify when I say multitasking is intolerable, I mean playing RPGs and doing something else entirely. If you're playing game and looking up spells for your next level or writing your backstory, that's fine by me. Your head is still in game mode. Depending on the game, I might even allow miniature painting, but that's pushing it. (The sort of game where I've seen that done in a reasonable way is 3.5 with long combats. When it's 30+ minutes between turns, putting another shade of red on your cloak is entirely reasonable.)