Living at home & sleeping in same room as your partner, is this still seen as wrong?

I'm a 27 year old male, and my girlfriend is 26, and we've been seeing each other for nearly 2.5 years now. Typically, our time together is spent with me going up to her as she lives in a house share, so we obviously stay in the same room. When I visit her parents, they're very chill and have no issues with us sleeping in the same room but in my house, my parents (specifically my mother) does not approve or want us to be sleeping in the same room. This has been the way it's been for myself and my older siblings whenever we've brought partners home for a night, so it's just always been the rules of the house.

This 'rule' is now causing many arguments between myself and my girlfriend as she thinks (admittedly somewhat correctly) that this is an outdated rule that shouldn't be imposed as I am in my late 20's, and my parents should get over themselves. She thinks I need to "grow a pair" and tell my parents what's what. I did speak to my mam about this and she just said essentially that it's just her rules and as long as I live there, I have to deal with it. Plus, my room is right next door to them so you can understand they don't want to be hearing anything, lol. And you know, she's right, and I do have to respect her rules as long as I live under her roof.

Is this kind of rule still largely a thing in Ireland with parents and their children, or is it a remnant of the past?