Non LGBT Related problem I need help with

I apologise for the off topic problem I'm about to discuss but I really can't find any other subreddit to help me out, the first one that comes to my mind is this one. And yeah I am gay, ( that's why I know this subreddit) but that has nothing to do with this.This is gonna be a text wall so get ready.So I'm friends with this girl, just for now let's call her Q. So I only recently became friends with Q and at the start she was really kind and caring and all. But now all of a sudden she seems to be rather mean. She criticises my every move throughout every day and it's just getting too much. It just hurts my feelings heaps.Today I happened to screw up my artwork ( I'm not a great art guy anyway) and she decided to make fun of it for a while, laugh at it and then use it as a punchline for when my other friends made minor mistakes on their work. I just had to sit there and take it basically. And this is only one example of what she does daily.It just becomes too much for me and today after that It basically drove into such a bad mood I was contemplating suicide. May seem a bit far fetched but I'm serious. It made me super upset and frankly I was holding back tears for the whole day. But I'm not the only person she upsets, she upsets my other friends a little bit too.All I'm asking for is a little advice on what the hell im supposed to do now.