I'm 20 years old and my mother still logs onto my FB and invades other areas of privacy.?

[Annie]

Depending on where you are, there could be options for treatment with therapy. You and your siblings should investigate this, just to see what your options are.
As for your mother, that is honestly distressingly messed up. She sounds incredibly controlling, and why is your father allowing this? You have two parents and he shouldn't let his kids be treated like this.
If you are not financially dependent on your parents maybe you should sever your ties with them for a few weeks just to show them the consequences of being smothered. If you are financially dependent on them it looks like you might have to just sit them down and explain how weird this is. Either way, get it sorted. Do you want to be a physician on your own or has she decided this for you too? You need to live your life now, because otherwise where will her controlling nature stop? Life is too short to be backed into situations like this.
Delete your Facebook and make a new one with a fake name, she never has to know. Try and make friends, you can easily balance study with a healthy social life.

Seriously, this parental behaviour is not normal, it's morbid. You should visit your local GP to get psychiatric help.