Advice needed for young teen daughter who wants to stay with abusive boyfriend

Hello. I am a mom who is totally unsure what to do and terrified that I'm going to make things worse. My 13 year old daughter started talking to a 15 year old boy 4 months ago. From the very beginning I have not liked this guy. He dropped out of traditional high school to do online school but brags that his mom does all the work. He lies and exaggerates very often.

Her dad and I (divorced) set some ground rules immediately that she could only see him once a week, either at one of our houses or at his house as long as his parents were home. We both spoke to his mom and let her know that was a requirement because 13 is too young to be alone with a boyfriend. She agreed.

Four long months later and watching her slowly retreat from all her other friends and all her sports and activities, I finally did something I never thought I would and took her phone and read through their messages. OMG. He was constantly insulting her, accusing her of cheating and worse, ignoring her, telling her what she could wear and how she could act, etc. Reading her responses where she apologizes, begs him to forgive her, and puts all the blame on herself was the most heart-wrenching thing ever. I also found journal entries from that time where she talks about self-harm and worse.

I took her phone away, tried to explain that she had been experiencing emotional and verbal abuse, and told her that I would not being letting her talk to or see him ever again. I also found a therapist that she has seen once and will continue to see once a week.

But she just does not seem to see the abuse for what it was. She cries constantly and tells me that she can't live without him, that nobody has ever made her feel so special, that she will wait forever. She makes so many excuses for why he mistreated her.

What can I do? What would you have been willing to hear at age 13? It hurts so bad to see her so devastated, but I know that this boy is such bad news and was slowly destroying her. Please. I ask for any advice.