Person w/o BPD, partner has PTSD, depression, and reasonably sure she has BPD too. 

Throwaway account, first and long post. I’m so impressed with everyone in this community and how honest they are with their struggles. Your posts have made me see my partner and our relationship in a much clearer light. Thank you for your courage. I know it’s hard. 

I’m hoping you can all help me now. Long post, partly venting, partly putting some thoughts in writing, but also need advice. 

My partner’s other support people are all toxic. She masks her feelings with everyone but a family member who was abusive to her, and a friend who seems deeply unhealthy for her. 

The family member is a huge trigger: anything other than a surface interaction causes massive emotional swings. Those are the worst times, but this is about the friend. 

Whenever anything challenging happens, she reaches out to this friend, who seems to trigger or actively encourage splitting (“you’re right that person is amazing / terrible / whatever feeling you have, healthy or not, I validate it and push you to act on it even when I know it’s not in your best interest and you’ll change your mind”). She’ll then ghost for days and leave my partner feeling even more alone, but unable to say anything. 

Whenever my partner interacts with this person she becomes more angry, sadder, and also more convinced her rage and sadness is caused by others (me / friends / bosses / work ppl etc) and she has no responsibility for them. 

Her (other non-abusive) family members and friends also think this person at best doesn’t have my partner’s well-being top of mind, and at worst are trying (consciously or not) to keep my partner unhealthy so they have some sort of influence in her life.   

I tried to talk to this friend in the past (before I saw the dynamic) and they freely admitted they purposefully avoid telling my partner the truth, that they think she is unwell / needs help, but they won’t ever encourage her to get help because it might cause a rift. They have also said (to me, never to my partner) the ghosting is purposeful to avoid any backlash and stay in her life. They also actively criticize or encourage badmouthing therapy / our therapists. 
 
For those who are wondering, there’s not a sexual component, but there is a “we are life partners” story my partner believes - this person massively over shares when they need something, but have their own family, friends, and social life they aggressively firewall from my partner. This person is core to my partners’ life, but my partner is a small part of this friend’s life. 

My partner has been friends with this person for years, and a big part of the reason is they 100% validate all feelings and encourage my partner to “be strong” and follow through on even her worst impulses. If it were just me who thought this, I’d be second guessing myself, but the fact others see a problem tells me this friends’ pseudo-support is unhealthy. 

I’m not sure what to do, wondering if anyone else has advice or experience with this. I don’t want to isolate my partner further: she needs support and really only talks to this person. Trying to tell her this relationship is potentially bad for her would not go over well - especially now (she’s in a really bad place, fully splitting or disassociating). But the current dynamic is degenerating my partners’ mental health and seriously impacting our relationship. 

Am I looking at this wrong? Am I missing something? I’m not going to pretend I’m right, but my gut and my sanity checks are all saying my partner’s recovery will never happen and our relationship will never survive with this dynamic. 

Any ideas / experience / help would be so valuable. 

Summary: my partners’ only other support person is a “frenemy” who seems to sabotage her well-being.