I (29M) have been with my girlfriend (26F) for two years and we have a really good and loving relationship. We were supposed to move in together the next few months.

My girlfriend and her sister grew up in a family where the mum was deeply abusive, to the extent that the daughters had to be sent to boarding school to get out of the situation. This has inflicted so much pain on my girlfriend, she suffers from very difficult anxiety as a result. In an attempt to protect her sister, she took on the role as the “first line of defense” against the mum growing up. This has made my girlfriend behaving like a protective mum for her sister, and she is extremely protective of her at all times.

Over the past two years, I have encouraged my girlfriend to go to therapy to find a new way to set boundaries with her mum. When we first started dating, I could tell that my girlfriend was under complete control of her mum. Her mum could call her to shout at her or guilt trip her at any time, and my girlfriend was always walking on eggshells. It’s a work in progress but she’s taking baby steps in the right direction to become an independent adult. She has just gotten a new job and we had started looking at apartments together.

A few weeks ago, her sister was admitted to grad school in our city and will be moving here in the next few months. Immediately, her mum started putting pressure on my girlfriend to move in with her sister instead of me. There were a lot of terrible accusations from her mum: that my girlfriend was a terrible daughter and sister and she threatened to cut off my girlfriend financially. My girlfriend stood her ground about wanting to move in with me, but I can still tell that she has been deeply affected by what her mum said.

Her mum has since then repeatedly tried to convince my girlfriend to change her mind. My girlfriend continues to say that she’s 26 years old and should be free to move in with her boyfriend (me) at that age. But I can tell that her mum’s manipulations are still effective over time: my girlfriend has started getting bad conscious about not living with her sister.

I feel like we’re screwed now no matter what. If my girlfriend and I live together, her mum will make my girlfriend feel bad for not spending enough time with her sister, no matter how much time they spend together. This inevitably goes out over the relationship between my girlfriend and I. We spent a vacation together with her sister previously, and even when my girlfriend and I got just an hour for ourselves to take a drink or whatever, she was still worrying about her sister (primarily because she was terrified her mum wouldn’t approve of her spending any time with me alone). This was terrible for my girlfriend, but also for me; I felt I was constantly drawn into their weird family dynamic.

So now that the sister is moving to our city, I’m at a loss. I don’t want to live with my girlfriend if she’ll be constantly worried about her sister (about taking the metro, making friends, being bored, you name it) as an extension of the abuse her mum subjected her to. It’s going to have an impact on my own mental health too if I’m drawn into this.

I grew up in a healthy and loving family. I have tried everything to help my girlfriend out of the abuse and establish healthy boundaries. But now I fear that her sister moving to our city will be the Trojan horse her mum desperately needed to reassert control. I know that my girlfriend is doing what she can to move on, but I also believe it can take many years for things to actually getting better. And it’s starting to have a real impact on my mental health, I’m feeling tired and exhausted.

I love my girlfriend but I want to have a relationship that isn’t, directly or indirectly, on her mum’s terms and a result of the abuse. And her ultra protective relationship with her sister has its roots in her mum’s abusive behaviour.

AITAH?