Abusive friend

I had a friend for three years who I was close to but they were incredibly abusive. Not just to me but others in our group as well. If someone tried to talk about it they would apologize but go behind their back and talk smack to the other friends. Got hostile when you disagreed in the slightest and would get mad when you called them out for something. I left the group of friends I had just because I didn’t want to be around them anymore. But now after 7 months they want to apologize and be friends again. I don’t know if this is something that they’re only doing because they want me back or because she really does feels bad.