Good advice from AnchorDownDeepBreath.
I fifth/six whatever the social media call out. We've often had a friend over for Christmas who has no family in this country. When she cannot come to us (she is in demand from other friends) like this year, I felt so sad she came for an early Christmas!
It is one day, make sure you get some nice food in and have a relaxing day. Then plan your future and what you want.
Of course you can stay in your home, regardless of what your landlady thinks, it is your home.
Your boyfriend being abroad without you, is it a serious relationship? If not, I'd get out there and make some new friends and see what the future holds.
Please take steps to get your money back from your mother.
I think the situation is serious enough to go no contact but some people prefer low contact, which means you will hear about major life developments etc.
I am so sorry your mum and brother are such shits. Can I just say as you get older you do make your own family, you find friends who mean as much to you as family, you'll maybe meet someone, 'settle down', have a family, whether you do this or not will be up to you.
Family can't dictate who you spend time with and what happens in your life once you are an adult.
Plus, your mum is a fool. She has picked an old lech over her own child. She does not deserve you. Get your money back and don't look back. I have a daughter, I would never pick a man over her.
en.wikipedia.org/wiki/Gaslighting