Scars
Master Don Juan
Only a beta male would allow that. A simple "No" would be fine.Then what if she demands to see your latest comments and posts? Because that's what women do.
First off, there should be privacy in your relationship, no matter if it's serious or just FWB kind of thing. Which means what you do in your private time & space is your business, thus you should not have to explain anything to her as if you were a schoolchild caught watching porno movie.
This is the equivalent of a girl demanding to see your activity history and messages on FB/IG. Alpha men would never allow this.
In OPs case, it sounds like the woman found out by snooping his history or search logs. He didn't "allow it", and he has no obligation to share his posts, username, or any of the sort. If a woman started snooping SS trying to find out my identity I would just say "Take a wild guess". But honestly, as soon as either party starts demanding the logins of social medias or wanting to read messages the relationship is over. There's no trust, just move on.