Update : AITA for grounding my daughter and canceling her senior trip after I found out she was cheating on her boyfriend?

Link to original post : https://www.reddit.com/r/AITAH/comments/1i50jtm/aita_for_grounding_my_daughter_and_canceling_her/

I received a lot of good advice from my original post and wanted to provide an update.

My daughter has been at her dad’s house since my last post. I called her saying I’m reconsidering cancelling her senior trip, but she needs to tell me what’s going on with this new guy, Brandon. She reiterated that it’s not serious and she’s just having fun. I told her she needs to decide which guy she actually wants to be with. She said she doesn’t want Brandon, but he’s fun and Jacob can be too serious and controlling. She likes how chill Brandon is.

She kept saying she doesn’t understand why I care so much, that I’m supposed to be on "her side", and that I’m acting like Jacob is my child, and not her. I told her that wasn’t the issue. The issue is that cheating is wrong, and she’s hurting Jacob, who she claims to love. She says she’s not hurting him because he doesn’t know about Brandon. I told her she’s going to have to tell him, and only then will she be allowed to go on her senior trip. She said she couldn’t do that. She still wants Jacob, but he can be annoying sometimes, and she needs a change of pace. I told her it was wrong to use both of these guys. I asked her if Brandon goes to the same school, and she said no, that he isn’t in school at all. I tried pressing her on how old Brandon is, but she wouldn’t give me a clear answer. She just kept saying he’s not that much older, but not in school.

After the call, I contacted my ex-husband to express our concerns about this new guy and how secretive our daughter is being about him. He told me I need to stop being a helicopter parent and let our daughter make her own mistakes and decisions about her love lives. I told him we don’t know anything about this Brandon guy, and how can he not be concerned about him? He said he trusts our daughter and that she is nearly an adult and that I’m just being controlling and projecting my issues onto her. I told him with how little we know about this Brandon and her not willing to at least break up with Jacob, there is no way she is going on the senior trip. My ex husband got upset saying I cannot make these decisions on my own and that she is his daughter too. He then he told me he’ll be paying for the full senior trip and that I need to back off if I want our daughter to ever come back home.