you shouldn't feel bad about it :'(
You were in the right for stopping being friends with them. Yes, you may feel really guilty, but in the end if it was a toxic friendship than you're only doing both you and the other end a favour by not continuing on with it. In a little bit you'll feel a bit better I think.
I'm not really much of a help, considering I don't have many friends, but I do want to try to make you feel even just a little bit less guilty or bad about it