Stop allowing these people to control you. Try telling her that she can stay but her boyfriend can't and then call the cops if he shows up? Seems like a good place to start. If she chooses to follow him, that's not on you Anon.

Easy. Stop being an enabler and evict his ass. You are not responsible for her choices. She is an adult. Tell here the things you said here face to face, and then evict him. Or, since it sounds like you are renting, have your landlord evict him. Although that may end up with you evicted as well. Did you tell your landlord how many people were living there? And another thing

how is it that you feel so responsible for someone that you have only known for six months? Have you sought psychological counseling for your issues? And how does your mother feel about this? Did she agree to

I'm thinking of a word. It starts with "en" and ends in "abler."