Hair struggles with daughter

My daughter has long thin hair that tangles very easily. She hates brushing it, and I always have to do it for her. This wouldn’t be too bad, except that I am divorced and she spends every other week with her father. When she is with her father, he doesn’t help brush it. So every time she comes back to me her hair is a matted mess. I have to spend literal hours trying to get it untangled again. A few times it’s been too much and I have to take her to the salon to get it untangled again.

I have been threatening for months that if she doesn’t start keeping it brushed that we will have to cut it. (Not too short, but around shoulder length.) But she loves it long and has an absolute meltdown whenever I bring up cutting it.

I already have single mom guilt. And in this case, I feel even worse because half of the blame is on her father. I have talked to him several times about the importance of helping to keep it brushed, but it hasn’t made a difference.

I’m really at my limit and want to cut it. Would it be too mean to cut it against her wishes?