'AITA for calling out my sister's BF's mom after she threatened to leave if they get married?'

"MIL Threatened to Leave If Her Son Marries My Sister – I Called Her Bluff. AITA?"

I (29F) need your honest and thoughtful opinions on a situation involving my younger sister (25F), who is under a lot of emotional stress just months before her wedding. I’m trying to offer her support, but I want to know if I might’ve been wrong in what I said. Here's the full context.

The Background: My sister has been in a relationship for 6 years with her boyfriend (27M). We come from a conservative family, so she didn’t tell us about him until she was sure she wanted to marry him. Once she did, my family met him, and we genuinely liked him. He’s polite, well-mannered, and clearly loves my sister. Within a few days, my family gave their blessing to the relationship.

So Where’s the Drama? Well, both our family and her boyfriend’s family are conservative, and to complicate things further, they follow different religions. My sister and I don’t follow any religion ourselves — we’re non-believers. But her boyfriend’s family is religious, especially his mother.

His mother wasn’t thrilled at first, but eventually gave her “approval” for the marriage — mostly, it seems, because of her son’s insistence. She had issues with her older son’s wife in the past (who is from the same religion), to the point that she moved out and started living with her younger son — my sister's boyfriend — full-time.

The Agreement: When discussing marriage, my sister made one simple request: she does not want to participate in any religious activities or rituals. She has no problem if the family continues with their practices — she just wants to opt out. Initially, the boyfriend agreed to this, and his mother seemed to go along with it. But it seems that acceptance was just a mask.

The Manipulation Begins: Not long after the initial agreement, the boyfriend’s mother began stirring drama. She picked fights with her son over my sister’s stance, questioning what sacrifices my sister has made for the relationship. She began guilt-tripping him, saying things like:

“So now there’s no place for our God in the house?”

“Who will carry our family traditions?”

“Will you always choose her over your mother?”

Despite my sister never demanding they stop their own religious activities, the mother played the eternal victim. And unfortunately, it started working. Her boyfriend, once supportive, began changing his tone. He started telling my sister things like:

“My mother is very innocent.”

“Can’t you just do the religious stuff for her sake?”

“You’re being egoistic.”

“I will marry you, but in the future I’ll only listen to my mother.”

“If things get worse, I won’t hesitate to leave you.”

This left my sister heartbroken. She's being emotionally cornered into a belief system she doesn't follow, and her boundaries are being slowly eroded before the wedding has even happened.

The Bomb Drop: When none of her manipulation seemed to work fully, the boyfriend’s mother made a final threat: She will move out and live separately after this marriage happens.

When I was told this, I calmly said: “Honestly, that might be a good thing for both of them.” I didn’t mean it with malice. But from everything I’ve observed — her emotional manipulation, her refusal to accept any daughter-in-law (even from her own religion), and how she uses guilt to control her sons — I feel like my sister has a better chance at peace if the MIL lives separately.

I later learned that the mother had previously fought with her older son’s wife too. When that woman called her out for being manipulative, the older son slapped his wife. The mother then moved out and now lives with the younger son, constantly poisoning his mind by saying things like, “Your older brother is already lost; don’t let this one (my sister) take you away from me too.”

Now my sister is crying almost every day, scared of what kind of life she’ll have — not with her husband, but with her MIL looming in the background of every decision. So… AITAH for saying that it might actually be a good thing if the MIL lives separately? I’m just trying to protect my sister, but I’m open to hearing if I was wrong.

What do you think? AITA? This is what commenters had to say:

PurpleGhost_87 said:

She should leave him, this situation is showing their true colors. MIL and boyfriend are both AHs, and your sister deserves better. Please tell her that she doesnt have to marry him, its perfectly fine for her to walk away and find her peace and the right one for her. Someone who will have her back and put her first.

Virtual-Swan-1253 said:

NTA, but that’s not the issue, largely because you were being observant, honest and correct. The issue is where the fiancée is in his stance on your sister participating in or contributing to the observances of her future husband’s religion. His change of stance sounds like a deal breaker to me.

Right_Cucumber5775 said:

Actually, your sister needs to cancel the wedding and everything. She absolutely should NOT marry into this narcissistic/enmeshed relationship. Sister needs to be clear that she will not be choosing religion, will not listen to and follow his mother's rules, and will not live with her. So, that will probably break them up.

Remind your sister she deserves to be treated with dignity and respect. Not second fiddle to MILFH. And if or when she would have children, it would become a thousand times worse. Who wants to live like that?

MerelyWhelmed1 said:

If the groom-to-be has already said he will side with his mother, then the wedding should not happen. He should marry his mother and let your sister go. NTA.

lapsteelguitar said:

“I will marry you, but in the future I’ll only listen to my mother.” This right here is the reddest of the red flags. Girl, do your sister a favor. Don't tell her to walk away from this relationship, tell her to RUN away from this relationship. Because she will spend the next several decades under her MILs thumb.

And Pretend_Artist_1823 said:

Your sister needs to leave now before they are married. He will make her life hell trying to please mommy.