Daddy at 21...

I'm twenty-one now, but there's this thing with a friend I've been doing for a while that started as just a silly idea. We met in college and ended up joking about age-play when we both wanted to let loose during finals week one time. It was more than a joke...it felt real. The first time we tried it, it lit something inside me. Being the older, responsible one...daddying her out seemed like just what I needed then and now, whenever she's down or stressed out. She calls me Daddy, dresses up in baby clothes when we hang, and I take care of her as if she were my own kid...but it's consensual, clear, all adult stuff. We're both eighteen plus and love these make-believe roles...so real it's hard to tell the difference sometimes. But today, something made me feel a little weird about this dynamic we have. Is there an age where being a daddy in such a close way becomes too much of a power imbalance? It feels healthy but also I'm not sure if we're just pretending or if my mind is making it real...what do you think?