Maybe she has given other guys hand jobs, but maybe she wants to change? You never know.
I also kind of agree with what other people have said, you're only 13!! Although I know a lot of men who started things early. I guess you can keep trying, but don't put pressure on her or anything, because then you definitely wont get one! When she's comfortable with doing it, then maybe she will do it. How do you know she's given other guys hand jobs anyway?
To love is to suffer. To avoid suffering, one must not love; but then one suffers from not loving. Therefore, to love is to suffer, not to love is to suffer, to suffer is to suffer. To be happy is to love; to be happy then is to suffer, but suffering makes one unhappy; therefore to be unhappy one must love or love to suffer or suffer from too much happiness. I hope you're getting this down.