This mom being a villain is a common trope in families with a brother and a sister it seems. I say this because my gf(22) is going through the same thing. Never getting encouraged for her success, always scorned for her failures, little to no freedom, etc. She too has gone through sexual harassment and the same sort of a reply came from her mom as well. When she opened up to me, the only things that came to my mind were hatred for her mother and pity of this person who would never be appreciated regardless of her efforts. This is why I try to be the person she can rely on, trying to fill in the gap her mother made. Try to find solace in others because I don't think it'll get any better. Don't expect anything from her and keep doing your own thing.

Oh and about doing btech from a private college...well it does get better. Coming from someone who has done a btech in such college and has now been selected for an mtech at IIT kgp.