I agree, it does sometimes happen without the resident parent doing anything wrong as such.
But that’s much rarer, in my experience. And to the teenager, it’s not for no reason.
Long heart broken texts to the teenager, suggests there may have been some codependency on the part of the parent in all honesty. Maybe the parent was so strict, that brought out a rebellion.
To the teenager at the time these things are very real and very difficult for a parent to navigate.
But ignoring the fact that these things are real to the teenager and focussing on the parents right to know they processed a move of college, prioritising how awful the people the teenager has gone to, propitiating the feelings of the parent and not self reflecting and not focusing on the teenager is not going to resolve it. And does suggest all may not be as well as the parent thinks they are.
But it is only a suggestion. Op may self reflect and genuinely feel they did nothing wrong. They may not have done. Doesn’t mean it’s not worth discussing.
I have an adult dd. If she has text me and said she was going to my brother, completely out of the blue I would have been concerned and wanted a further gentle discussion. Op had no issue with that, so it maybe something that happened a lot. It would raise a red flag for me. But I would have asked if they were ok, confirmed that’s where they were and allowed some space. If she stayed, my focus wouldn’t have been on what I believe my rights are. That in itself is a red flag.