My relationship with my mother (50) is crumbling because I want to move in with my bf

for context, my mum and i never had a good relationship. It all started when i was about 13. We argue almost weekly and it would last days as she would ignore me after arguments. My dad was never really in the picture ever since i was 10 and he was verbally abusive and abused substances and me being the oldest child, experienced most of his abuse so i’ve had a bad impression of him ever since i was young. My mum knew about this but still continued to push me to have a good relationship with my dad because “he’s still your dad” and it frustrates me so much. My mum is also someone that I can’t confide in because she’ll use it against me one day in an argument. For example when i was younger, i’d get in petty arguments with my friends or brothers and as a child, would cry about it to her and to this day she says that it’s my fault for feeling lonely because i like to argue with everyone. My brothers and I don’t have the closest relationship at the moment and im pretty sure it’s because of her as well, as she’d usually tell my brothers whenever we have an argument that “your sister is so sensitive” or “your sister is just like your dad, she’s crazy”. She also likes to control me using money or whatever she has over me, so if we argued the past day and I needed money for something she wouldn’t give it to me, or sometimes she wouldn’t even drive me to school (not walking distance) so call me an asshole but sometimes I just had to lie my way out of things.

Right now im studying abroad and our relationship has healed ever so slightly, but it’s still shaky. I’m 20 and have a boyfriend, who she doesn’t really like not because of him but because of the fact i have a boyfriend. My boyfriend and I were thinking of moving in together to save up on rent as my monthly budget is only 860€ per month and gas and electricity prices here are increasing. I told my close friend about how nervous I am for my mums reaction if i were to tell her, because I knew that it would only mean chaos, so my friend told me not to tell her, and i agreed. One day when i was on the phone with my mum she brought up something about housing and if i’m looking for any which i hinted that i might want to move in with my boyfriend of 2.5 years. She was furious when she heard, and started yelling at me through the phone that I was “selling myself away at such a young age” and that I made myself sous cheap because “i was moving in with a guy for money”. I tried explaining that he was my closest friend abroad and the most reliable person right now and not just some random guy, and that we’d be saving a lot of money in doing so as well. She continued to yell and bring things up from the past, calling me a disappointment of a first born and that I betrayed her values. She kept on bringing up the point that she’s a single mother and works very hard for me (which she brings up a lot and me and my siblings understand and are very grateful for) and that because of me she would have to work another 20 years before she could retire. I thought that saving up on rent would be a decent idea in relieving some burden, and i do plan on getting a job soon (it’s just currently my visa does not allow it) but she refused and said I was betraying her values and she cannot support this decision, once again and continue to yell about what a disappointment i am. I don’t know what to do and honestly that argument left me shaking and crying in my apartment trying to explain myself to my mother, emotionally exhausting me for the next few days and I refused to pick up her calls after that. I know i’m not in the right completely here but is 20 really too young to move in with my bf? I feel like my relationship with my mum is soo far gone, i don’t know what to do.

ps. sorry it’s not written so well, this situation is kind of a mess and hard to put into words.

tldr: mum and I have bad relationship. mum is upset that i want to move in with bf and argument ensues