Since you are helping her, she pays for dinner. Anything you get on top of that is just bonus for a job well done.
Got it? She is paying for your time, bro. Please do not be like the typical frustrated guy, go against the grain and women will respect you for it (even if they say the opposite).
I was dating this girl about 2 months ago and after she gave me the "it's not you, it's me" spiel, I stopped talking to her. One time she wanted to watch TV on her computer but couldn't figure out how to do it. I said I'd help only if I got dinner in return. I helped her, she took me out to dinner and paid for it (not cheap, not very expensive either).
Since then, I haven't spoken to her. Did she use me? No. Did I use her? No.