Long story need advice

So my bestfriend(j) is a junior in high school his gf graduated last year. Me and j are in one act play together. I’ve been acting 8 years and take every direction I get from my director very seriously. We play an old Italian couple in the play so of course he has to do things like put his arm around me. The other day while we were performing his gf started screaming from the audience. We later found out she was screaming “that little slut” to me . She then texted MY TEACHERS asking if me and j flirt and she told my teachers I’m a “terrible/ problematic person” then she went offffff on j because she didn’t like that we are in a show together. I hate to see my friend in such an abusive relationship. I already texted her and told her to grow up( this girl is 19 and I am 14) and she keeps talking crap about me saying I’m a slut idk what to do. Did I do something wrong?