Reasonable means that whatever decision was made is appropriate given the particular circumstances, and most would regard it as so.
Justified means that whatever decision was made is done for a good reason, in the interest of fairness.
There are times the words could be used interchangeably, and contexts where the difference is subtle. It all depends on the nature of the request or issue at hand.
I might use "justified" if I was angry about something, and was acting in response:
Was it polite to skip their wedding after they insulted me like that? No, but I think my decision was justified.
I might use "reasonable" if I think everyone would agree that there was nothing else that could be done:
Was I happy about missing their wedding so that I could go to my mother's funeral? No, but I think my decision was reasonable.
But there are contexts where either word will work just fine:
You said that you'd deliver the cake before noon, but it didn't get here until 3 o'clock. I think my request for a refund is reasonable/justified.
In that sentence, reasonable would work because most people would agree that a refund would be appropriate given the circumstances, and justified would work because the request is fair.
There is a bit of a difference of the two. When you use "there is" as you did in the first sentence you stress that something exists. In contrast, when you use "It is" in the above example it is a bit different. "It is" seems to refer to something else that you mentioned earlier in a conversation. If you had been talking with a friend on the way to the train station about how every day there is a different conductor it would make sense to say "It is a lady conductor today". However, if you hadn't mentioned anything about the conductor previously it would sound a little odd. It would sound like you were thinking about something earlier, but didn't say anything about it. It would sound disconnected.
Best Answer
"Lady" can be used to refer to someone of higher or lower social rank. When it's spelled with a capital letter, it is the title of a woman with the equivalent rank of a Lord, or a woman who is married to a Lord. As "just a word", though, it usually refers to somebody who is of a different social rank from yours. You would use the terms "cleaning lady" and "bag lady" just as much (and probably more in these less-formal times) as you would "lady of the house" and other sorts of "you are more important than me" phrases.
One needs to watch the use of "lady" these days. Because it has been as much a word that comes automatically with marriage as one that may be earned, it is sometimes felt as belittling, dismissive or condescending; something like calling Jane, who is married to John Smith, Mrs. John Smith. The word itself isn't a bad one, and can be used in very positive ways, but many of its uses—uses that once would have been the height of proper manners—are very much unwelcome these days.