Okay so first off, how old are you and do you live in your mom’s house? Because if you’re living under her roof and she’s paying the bills, she kind of gets a say in who stays there whether you like it or not. I know that sucks to hear but it’s just how it works when you’re not the one paying rent. Like, my mom would never let my boyfriend move in either and honestly I can’t even be mad about it because it’s her house.
But if you’re an adult and you’re contributing to the household or paying rent yourself, that changes things a little bit. You should be able to have a conversation with your mom about why she’s against it. Is it because she doesn’t like your girlfriend specifically, or is it just a “no partners living here” rule? Because those are two different problems. If it’s about your girlfriend personally, that’s something you might be able to work through. If it’s a general rule, you might just be out of luck unless you’re ready to move out on your own.
The real talk here though is that maybe it’s time to start thinking about getting your own place. I know that’s easier said than done because rent is crazy expensive right now and everything costs money. But living with your mom and trying to have an adult relationship at the same time is always going to cause problems like this. You can’t really be independent while you’re still depending on your parent for housing. It’s just a weird in-between place to be.
Have you tried asking your mom what her actual concerns are? Like, don’t just argue with her about it, actually listen to what she’s saying. Maybe she thinks you’re too young, maybe she’s worried about the relationship being serious too fast, or maybe she just doesn’t want extra people in her space. Once you know what the real issue is, you can either address it or accept that this isn’t going to happen and start making a plan to move out. Either way, getting mad and fighting about it probably isn’t going to change her mind.