friend issues

So, for a couple of years some of my ex-friends have been bullying me (emotionally and cyber) . At the time they were also bullying a girl I'm still friends with now who was also in the friendship group(imma call her Becky). Becky told me about how she felt about them as I was starting to come away from them so Becky, me and another girl left the group and eventually found a new friendship group. Things were fine until Becky started talking to one of the girls who was one of the main ones bullying her and I again. I asked her why and she said she never actually bullied her just teased. She started hanging out with all of my ex-friends constantly and just kept claiming it was fine. But I knew things weren't fine becuase occasionally she'd come to me crying saying they was bullying her again but then go back the next day. This went on for a while and I stopped caring until Becky tried making me hang around with them again. She'd beg me to come and talk them almost daily and we kept falling out over it. Every time I asked her why she'd respond "they didn't actually bully you, I've been bullied in the past and they weren't bullying you." it really hurt me so we stopped talking for a few months. Eventually, we started talking again and she's still hanging with them. She stopped trying to get me to hang with them but after a few months started again. She'll try and make them sit near me or even try and get them to talk to me whilst we're mid conversation. I kept telling her to stop trying to get them to hang with me and if she wants to talk to me I don't want to be around them. Becky said she can't becuase she has attachment issues from her past. Whilst I do understand that she has had issues in the past, I l've had a hard time believing it becuase this has never happened with any other old friends and she constantly lies about the randomist of stuff. For example, she kept telling people she had an ankle issue (not true) but told everyone different ways of how she got this ankle issue, some were falling off a bike, being born with backwards ankles or it just happening overtime.

So basically, what I'm asking is, what should I do? Do I just leave her to be unhappy in the other group and ignore her trying to make me hang with them? Do I cut her off completely? And if I do try and get her out of the other group, how?