How much should I pay for grad photos?

Hi! Sorry if this isn't the place to ask this, it seemed like all the rules and posts were from the perspectives of photographers, and I am a would be customer but anyway. So I'm in college and there is this girl in one of my classes, she's 17 and mentioned she's been trying to get into photography and was showing me and other classmates some of her work she's done with her friends. She mentioned she's trying to build a portfolio. Well, I graduate this fall and want to ask her if she's interested in doing my grad photos. If she is, and doesn't ask for any specific amount, how much should I pay her? Of course I want to pay her for her work but tbh the only other time I've had photos professionally done was for high school graduation and my uncle paid for it without telling me anythjng, so I have no idea what pricing is like in the photography business. Thanks!