My friend is 19. Her mom tried to choke her and kicked her out of the house. Can they kick her out if she is still in school with no way to support herself?

It sounds like a very serious situation.

The first thing to do is to encourage her to go to the police to report the assault. They can then help her contact Social Services (or whatever they call it in your area) who will help her find a safe place to live.
If she has reached the age of majority, her parents can probably ask her to leave, but it wouldn't be a thing that a smart parent would do. They certainly cannot implement this by assaulting her!!

I hope things work out for her and I am glad that she has a good friend to try to help her.

Yes. the magic number is 18, the age of adulthood. domestic assault covers your other question. the police should have been called at the time this occured for two reasons 1. to make a report 2. to check for physical evidence on her body of an assault 3. to arrest or advise options for order of protection, restraining order, etc. if your friend has maintained residency at her mom's home.....clothes, personal belongings, etc., then an order of eviction is in order and a 30 day eviction notice will be served on your friend. by the way, what did your friend do that caused this assault??

she can press charges.....but she can't stop them from kicking her out and not supporting her...she is over 18......what did she do to provoke such rage in her mother????? sounds like 'she bit the hand that feeds her'....no excuse for a mother to act such a way, but I am 99% sure she was provoked beyond her control.......
parents owe 19 yr. olds NOTHING...kids now a days just feel they do, entitled.....they never ever stop to think what they owe, respect and decency wise , to their parents.....