Do you live with your mum OP?
I think you need to start putting a bit of distance between you. I am not saying cut her out etc.
Just some distance, she won’t change so no point trying.
Next time she says something unkind say, if I want your opinion I’ll ask for it thanks?
Start joining some classes, whether you are interested or not. Not to make friends as that just puts pressure on but to keep busy.
Tennis or Golf are great socially
Walking groups, pottery classes etc all fill in time.
In the next week give yourself a task and sign up for 2 classes. Don’t tell your mum, if she asks where you are just say out.
You need to slowly but surely untangle yourself. Don’t get into the spiral of blaming or being angry with your mum, work on yourself and your response. Take ownership for your life.
If you go down the road of therapy, a good therapist will show you how you’ve been conditioned and how best to untangle yourself. A bad one will focus on labelling your mother and her behaviours and you will never get past this and live YOUR life. Choose a therapist very carefully
OP, just live - set up these classes / groups. Don’t think about it, just jump in !!!!!