US expatriate but remaining in US while attending university

Hi,
I am looking into this for a friend. We are both dual citizens, but she got naturalize when she was 15 via Birth Abroad (Now 23), born in Canada. She is having to renounce her America citizenship but she wants to be able to still attend post-secondary school here. Preferably as a non-resident alien, or something that would allow here to have in state tuition because it is so expensive other wise. I have no idea and was unable to give her any advise on what she should do...If there are any visas that are advisable to expats? Anything would be helpful at this point.... I don't want to see my friend leave the country!

Why would she renounce citizenship only to return to US? Sounds fishy.