I have a fwb who is socially aware and intelligent. She recently has started mirroring my behavior. She's started agreeing and amplifying when I agree and amplify, slow responses, even soft nexting me if I soft next her, and doing texting for logistics. I hang out with her often but don't prioritize hanging out with her, often I'll bail to hang with friends or study. She has now started doing that as well. I'm naturally a stubborn guy and now she has started matching my stubbornness. She's even implementing dread by casually mentioning other guys.

She used to not do this and was just normal.

My theory is it could be two things, the first being decreasing interest in me or my frame is slowly eroding (or both). The second explanation being she has realized my behavior is increasing her interest in me, so she is trying to replicate it to increase my interest in her.

I am leaning toward the second explanation as we still hang out and have sex often and she is affectionate toward me when we hang out. She has started saying she loves me, but only in-person. The sex is getting a lot better as well. Maybe she wants a relationship with me and is trying to get me to put in more work. I suspect her friends are coaching her, but it is likely she has figured this all out herself.

Despite the great sex, this behavior is annoying to deal with so I plan on demoting her back to plate shortly. In the future, what can I do to prevent this from happening with the next girl? Any of you deal with this from a fwb/plate?