What’s the smoothest response to this?

I need help figuring out the best response to this thing this girl keeps saying to me. So to start off the story, I was in school and went to the wrong bathroom on accident. When I walked in I saw this one bad female and she was like putting her belt back on but I was just like oh shit wrong bathroom and walked out, and I heard her start laughing. So later that day when I was going up the staircase she hit me and was like “oh did you have fun in the ladies room earlier?” And I just said something like, “a little bit”.

Now every time I see her she says “oh this isn’t the ladies room” or she brings it up to me and other people as a joke like “yeah he came in the ladies room when I had my pants down and belt undone.” And I’ll just go along with it, but i need a good response to escalate the situation. I was thinking saying something like “sounds like you liked it” was good.

Now I goto a small school and it’s just a different environment I’m not used to escalating in because it’s harder since I don’t have my car here and you can’t really be in other genders dorms. But anyways I’m pretty sure this girl is interested in me, and I don’t wanna Date, I’m really just trying to fuck cause I know she’s already fucked w someone I know.

What’s a good response I can come back with to escalate?