Hi Myfiancesmom
Welcome to the BPD Family
I'm sorry your girlfriend's mom is causing trouble between you and your girlfriend. It sounds like you've walked into something here that the two of them have been doing for years. Because they have been doing this dance for years your girlfriend may not know another way right now, but if she's open she certainly can learn some new tools for dealing with her mom. I do want to say here that it is up to her if she wants to make changes in the relationship with her mom. We can only change ourselves we can't change other people... .you can provide her with information or you can even direct her here if she's interested but you will not be able to make her or her mother behave differently that will be up to them.
I think the best way for you to get started is to learn about BPD we have a lot of information on our website so I'll pull some things that I see in your post to get you started.
I hear several things going on, I hear enmeshment of your girlfriend with her mom. Here is a link to more information on enmeshment
https://bpdfamily.com/content/was-part-your-childhood-deprived-emotional-incestI hear emotional blackmail... .we call it FOG (Fear, Obligation, Guilt) Here is a link for more information on FOG
https://bpdfamily.com/content/emotional-blackmail-fear-obligation-and-guilt-fogYou may also be stepping into a Triangle with the two of them that is not a healthy dynamic and you will want to try avoid being a part of the triangle if you can.
https://bpdfamily.com/message_board/index.php?topic=108440.0 Beyond the links I've provided please see the box to the right -> each item is a link to more information. You might want to check out the "Lessons" section.
It's great that you are reaching out on behalf of your girlfriend it's obvious that she means a great deal to you.
I would be interested to hear about what you think after reading some of the material on our site.
Take Care,
Panda39