Disclaimer:
Am not a tax professional by any means.
No, you don't have to claim her. However, it's in your benefit to do so, generally.
I have the same issue. Kid in college. She works, but not much. She has hardly any taxes taken out (she earns too little).
I claim her as a dependent, I get a deduction. If I don't, then I can't. I get a bit more money by using her as a dependent (and all that entails) than she could ever get on her own.
And that, is the key point. If you get $5k worth of deductions (not to mention tax credits for education, etc.), then why would you allow her to file (she won't itemize, she doesn't have enough to do so) to get $500?
My $0.02.
fret