What should I do ??

Ok, I have recently left a group of friends that were giving me loads of hle. So, it is has been awkward whenever I p them in the corridors it is weird. Everytime they are with someone that I goto, they storm off e.c.t... I've been civil about it. Ok, so in music, I was sitting beside one of them that I'm kinda friends with. I went "What is wrong with her face ?", towards one of the other members in the group that was in the cl. I never ment it in a harmful way, it just came out wrong and the person that I'm kinda friends with went all straight faced and moody. I went,"What is wrong with you ?" and then she went,"I don't like it when people make fun of my mates, I'm not going to shout at you or anything ... just saying ..." I said I was sorry and she said it was ok, she seemed to forget it as the day went on. I'm still depressed though, as if I'm worried about it or something. Should I not worry about it and not worry incase it gets back to her ???