Girlfriend's friend has BPD

[OutOfEgypt]

Hi everyone,

Not sure what forum this even belongs in, so I'm posting it here. 

I'm in a relationship with a girl whom I really like.  We've talked a lot about relationships, and it became pretty clear to me that at least one of her very close friends is BPD (possibly two).  In fact, I found out that this friend, let's call her Jane, was diagnosed as BPD and was told by her T to come back when she is serious about getting help.  My girlfriend has noticed strange things about Jane and their relationship, but she really didn't have much of an informed idea about BPD.  Talking to me about these things has been an eye-opener, the "scales fell off" her eyes, so to speak, and she has recognized a lot of pretty disturbing things that she formerly overlooked (like all of us, at first).

This, naturally, has led my girlfriend to seriously reconsider her friendship with Jane -something she was already considering before I met her.  She knew something was "off" but couldn't put her finger on it.  Well, now that she is distancing herself from Jane and even telling her, "I'm not sure I want to be friends," this is obviously triggering Jane.  In fact, even before these talks they've had, the fact that my girlfriend was talking to me much more and spending more time with me was already triggering Jane.  But now it is even worse.  I'm not talking about violence or anything like that, but strange and manipulative things that we are all familiar with... .stealing my girlfriend's wallet and then pretending to find it so that she can come over to my girlfriend's house and be with her, endeavoring to drive my girlfriend somewhere but then taking a "detour" so they can be alone, in the middle of nowhere, and "talk."  My girlfriend has also noticed how Jane has done things to alienate her from her children, in some cases.  Overall, there's a lot of odd behavior, a lot of inserting herself in the middle of situations (she's used to being allowed to ALWAYS be around).

One incident made things pretty clear to me.  Jane came to pick my girlfriend up from my house, and as I was saying goodbye I wanted to give my girlfriend a kiss.  Jane got out of the car, stood there, and watched us kiss as if to protest.  It was really awkward.  It doesn't help that Jane may be either bisexual or a lesbian and, from what I can tell, is in love with my girlfriend.

And my girlfriend is going through her own growth process with this, realizing how much of a rescuer she is, buying into Jane's pleas for help and lament over how "everyone leaves" her, prompting my girlfriend to think that all that Jane really needed was someone who loved her like a sister and never gave up on her.  Well, she is learning how in some cases that is the worst thing.

To make matters more complicated, my girlfriend is friends with Jane's mother and sister.  So, even though one would think I'm an "expert" because I've been through this, I still am at a bit of a loss as how to advise her.  The big main difference is that this isn't a romantic relationship (though for Jane it may be), it is only a friendship.  But it is clear that the more open and honest my girlfriend is with Jane about things and about the possibility of her ending the relationship, the more Jane clings... .endless calls and text messages in the night, swinging from playing victim looking for sympathy to being angry and accusing toward my girlfriend for not playing along, manipulative behavior, etc.  Jane has also begun latching onto one of my girlfriend's friends (another rescuer-type) who may actually allow her to move in with her.  And certainly, we both anticipate that Jane will seek to use this other friend as support while demonizing my girlfriend.

So what is the best approach?  Should my girlfriend just do no contact?  If she isn't willing to, how should she handle it?  Tell her the truth and tell her to get lost, or should she act as though she's "confused", as one of the articles says?  My girlfriend won't like the latter as it is being dishonest.  She isn't confused one bit!  She just feels badly but knows it is not healthy.  Thoughts?