Girl said she wanted to beat me up..?

I used to be best friends with this girl a few years back in school, we weren't very similar as she was reeeally badly behaved and was quite aggressive in a sense but she was a lot of fun and lovely. But about 5-6 months ago when I hadn't seen her in aaaaages cos she went to another college she was talking **** to my friend right in front of me and I butted in and had a go at her. We then had an argument on Facebook and I tried to say sorry but I was being kind of rude about it... She said she was gonna come talk to me at my school but she never came lol... But then about 3 or 4 months ago my friend who she occasionally still argues with told me that the girl said that next time she sees me she wants to beat me up, I don't really know if she's just talking sh*t or she actually would, especially if she's with a friend, basically, WHAT SHOULD I DO? I was thinking of maybe apologising to her on Facebook chat and to ask to be neutral but idk if I should or not... Sorry for how long this was but yeah please help me! Thank you