I share mutual friends with my ex BPD who cut me off 3 months ago. Whenever I engage with friends in a mutual discord server she pops out of nowhere and start engaging with the same people / likes all their posts but act like im not there(not straight away but hours later). 

If I stop talking in said server and disappear for a week or more, she also disappears but reappears and posts again whenever I post again in the same server. She also mirrors the way I talk when I post, everything down to the choice of words/slang that I use. Have also noticed shes had her profile set to offline now ever since we broke up but use to always show as online in the past.

Can any explain this behavior? I dont know if im overthinking shit and just being paranoid but something just feels off