how to work with someone you hate on a three week project and they think your are friends when u used to be but now arent?

There is a girl who thinks were still friends but we kinda drifting away cause she is toxic and I don't wanna be her friend. I can't tell her in class while we work together because she starts a fight everywhere and I am quite innocent so I don't wanna be in a fight . Even if o tell he realy nicely she will still start a fight. Now we have to work together on a stupid 3 week project and i can't stand her I don't wanna work with her because I am not her fiend and she keeps trying to engage in conversation and then she asks me why IM ignoring her what do I say to her . I can't say I'm not ur friend cause she will start a fight right there ( she thinks were friends but I'm not her mate)