My 19 year old has been involved with a 21 year old for the past 4 years, now this boy has been beating her up. It may be after their both intoxicated. I have tried to convince her to go to the authorities, but she refuses. She stays at his house most of the time and returns home to shower and eat.

What a terrible recipe for disaster if ever I heard of one ! Throwing her out would only make it worse, summer. You don't want her there with him permanently, you may not have a daughter anymore, alive.

She needs to see that is not a proper relationship and get out of it.

Tick

Have you tried telling her his house or mine?
How is it effecting your home life?
If it is really chaotic and you have to throw her out it is important that if she will not leave willingly when you tell her you want her to leave you have to go through the legal eviction procedure for your state.

I agree with Tickle that you really need to weigh your decision.

I wouldn't throw her out! She may only be able to eat/shower when she comes home to your house. You may be her only get awaay. If you toss her out like trash something even worse could happen

I agree that throwing her out will only make things worse. She'll move in with him, and things will get far worse. Being drunk is NO EXCUSE for hitting ANYONE, much less someone that you claim to love. Have you tried an intervention? Have you tried reporting him to the authorities anyway?

Does he have a past domestic violence record?