Is it normal to put a girls hair in your wallet?
What? No, that's definitely not normal.
But what if she has really nice hair?
Still, you could just compliment her. It is wrong to take some of her hair for your wallet.
And if I do it anyway?
Well, it would be really creepy if you did and if she ever found out she would do anything to avoid you. Doing things like that can label you as a stalker and I'm sure you don't want that.