Hi Guys,
I'm really struggling. Before I started dating my current girlfriend who has been my friend for over six years, I welcomed both her and her girlfriend into my social circle.
Along the way I introduced this person to people because she had no friends other than our girlfriend and I felt bad for her.

Anyways, fast forward a year and my girlfriend and this person break up. We begin dating but not immediately. During this time they are still living together until the ex finds a new place.
The more I talk to my GF she tells me she believes her ex is histronic. This woman hits on everyone. Huge flirt, extremely inappropriate behaviors. Well about a month after the break up she sends my girlfriend a letter pretending to be me. Pretending I'm stalking her and in it I confess to breaking them up.
That's all I needed to know to know this person is not healthy and I tell my GF this.
While in my social group (I run) I had introduced my exes ex to a woman who I think overall is nice however she is bringing my exes ex to functions I decline so my entire social circle is now hanging with this loon.
I know it's not my place to tell anyone who they should hang out with but this is bothering me greatly. This woman also went to some good friends of my girlfriend's, two different families that live on a lake (my girlfriend petsits for them) and told them she only hangs out with them for their money and the condo one of the families let's her use in California (once a year vacations).
THAT is not my GF (a user). The sad thing is one of these couples immediately writes her off for trashing my GF, their longtime friend, while the other feels sorry for her and still welcomes her in their home. This woman lives two states away, can't she get her own friends? No.
My tolerance is not what it used to be. I'm at a point I can't hang with people knowing they are a direct link to someone who pretended to be me and never apologized or denied, nothing. People just ignored it and they still speak to her. Isn't that nuts? I'm not sure how I should handle this. Right now I am stewing in silent resentment but I figure that's more mature than blasting her to people who think she's "normal".
This has also put a strain on my current relationship because my girlfriend has not unfriended this woman. Her reasoning is, why cause more drama? If she reaches out it's once every six months or so and it's brief.
Do I have reason to be upset or am I overreacting? This woman actually began hanging out with a HS friend who started the social group with me. This friend no longer speaks to me and for awhile was sneaking around with this woman having her housesit for her and her husband (their dog) not saying a word until I confronted her.
I just feel betrayed in so many ways. I'm about to break up with my girlfriend just because I want this person who is not physically in our lives out of it. I feel I need to respect my boundaries but am I taking things too far and over reacting?
I feel I have a heightened sense of awareness when it comes to people with disorders. I want to get as far away from them as possible but am I ruining my life by pushing away people who associate with them even if it's just socially?