I (23M) went through my GF’s (25F) phone and found something. Should I tell her?

My (23 M) gf (25 F)has a professor (50 M) that she talks about all of the time. Really seems to be into the guy. She talks about him so much that even her parents talk about him while I’m at their house. Her friends also joke that she’s in in love with the guy. I asked her about it and

This bothered me so much that I kept asking her about him and she’d tell me, “no that’s gross he’s old” but she’d smile and appeared to be obviously lying. I could tell the thought of him exciter her. Eventually I felt I had to go into her phone while she was showering just to find out the truth. And sure enough she posted erotic fantasy articles about him 11 months ago before we got together (3 month relationship). These go into extremely graphic detail that I regret reading. But I can’t unsee it now.

I dont know if I should bring it up to her since it was 11 months ago, but she has 2 classes with him this semester and I can’t help but think that she still has these fantasies. She talked about staring at his genitalia and picturing him bending her over his desk. Just that kind of stuff.

These feelings don’t just disappear and it worries me. But I can’t tell her without also admitting that I snooped through we phone. Should I tell her or just push through it?

TL;DR: gf used to post erotic stories about her current professor and I found out by going through her phone. Should I tell her I know?