Learn English – “What’s her” vs. “What’s hers”

Yes, it's fine. You can use multiple pronouns as long as they don't create ambiguity. In this case, there should be no ambiguity as yours must refer to the listener, while hers must refer to a third (female) party.

Even a sentence like the following is grammatical:

They both have good cars, but his is better than his.

To make this sentence unambiguous, though, you would have to point or gesture toward the people you're referring to as you say the pronouns aloud.

Really, it's just a matter of making sure you're communicating clearly.

Nothing to wonder there!

This is my friend
That is yours, and
Here is hers.

Likewise...

Friend of mine
Friend of yours, and
Friend of hers

Hers -pronoun's possession.

Do you know a friend of hers ~ Yes, I know a friend of hers (fit in the above example).

The sentence reads a friend of... and is singular. Hers there is as defined above.

Good points to note are CopperKettle's and Oerkelens'.