It's okay if you aren't into having things around your butt, but also getting fucked by a girl is only something people who are attracted to girls would do. A lot of men exist who just flat out refuse to even think about it as if they will lose their masculinity or catch the gay.

This seems to be something that she really wants to do. She probably thought it was hot and was interested in trying it with you. You'd have to ask her about it rather than us.

She might be remembering the fact that she did the same thing for you in the past that she didn't entirely like and feel like you should do the same for her. She might just want to explore like you did.