So, she treated you badly, you had to end it after being strung along and she wants to come back after finding out that her number one choice won't deal with her shit.

Come on man. How are you going to look in the mirror in twenty years and feel about that if you take her back?

Is that the story you want to tell your grand kids?

Will she just change her mind again when another option presents itself?

It sounds like your life is going well and you are about to drag an already identifed hazard right back in front of you.

She already mucked you around for at least six months, plus the emotional shit you went through. This is her. She did that. And she's not magically all fixed now.

Is this what you want? Really?