A little background to start is that my significant other and I have been together almost 6 years. We've been living together for a year and a half and I am 39 years old and she is 35. We plan on getting married and have a wonderful relationship however, starting 6 months ago and as recently as last night she is exhibiting some really disturbing behavior and I'm not sure how to handle it or what to do.

She comes from the best example of what is described as a narcissistic family I've ever seen and her mother, an obvious narcissistic mother, rules her and her siblings with the authority of an all powerful dictator. They are all adults aged from late 20's to Mid 30's and two of them still live with the mother. To give an example of the level of enmeshment the mom has I will just say that she is completely intertwined with 3 out of the 4 of them and has full control over all aspects of their lives. Her youngest son, the Golden child, while showered with gifts and provided with anything he wants (as long as it's not something that would enable independence) cannot keep a relationship as his mother has decided he can't have sex until marriage. He is 28 so the fact that he can't even spend the night somewhere with a girl is not viewed positively by girls he dates. The mother also still is on all of their bank accounts and credit card accounts with full control over them. My girlfriend cannot change this due to fear of the repurcutions. Since my girl is the only one of the family to have resisted the enmeshment she is the black sheep. This is manifested by absolutely no assistance in life whatsoever and complete indifference to her life outside the mother's house. My girlfriend MUST spend every weekend at her mom's with her family. I feel like they need to feel that technically she still lives with them. That our apt is solely to be close to work. Also we cannot tell her mother we are living together as she does not believe in anything before marriage. Her views on life are imposed on her children and they are mandatory. This has resulted in identity and self esteem issues for all of them.

Having given a little background info I will get into what my girlfriend has started doing. Six months ago she finally confided in me about her mother's psychological abuse over her entire life. This mainly consists of criticisms or forbidding all interests not associated with herself. Imposition of the mother's life beliefs and adoption of these being mandatory. Complete unwillingness to emotionally connect or even respect the feelings of her daughter. Almost like she has no right to have them. Refusal to communicate and constantly sowing confusion. Passive aggressive comments and actions. Feigning ignorance of the most blatantly obvious examples of these things. Confusion, word play, and gaslighting being her go to tactics. My girlfriend has researched this and she talks and vents to me about it. Lately if she vents about her mother I can expect that within a few days she is going to feel guilty and what she does is she will start treating me exactly the way her mom treats her. Now she's told me how her mom is. So her doing the exact same thing to me, given I'm aware of how her mom treats her, is baffling because I see what she's doing. I'll call her out and have done lots of research on narcs and she will just keep doing it. It's as if she's trying to recreate the dynamic but this time play her mother's role. Now given that she's told me about her mother and she knows I'm knowledgeable on narcissists and their tactics (cause I point them out when she does them) what scares me is why is she attempting this? Is this a biological thing that she just can't help? Because I'll call her on it which I'd think should kinda trip it up yet she will just try the same narcissistic tactics over and over.

Sorry for the novel but is she biologically incapable of not doing this? What are my options?