Yes, because your daughter IS the one who sacrifice herself for your happiness.
Sacrifice my ass, Mahoro's happy where she is right now. She saved her grandmother's house, she lives with her friends and has a fluffy slice of life existence there with them.
I feel bad for the father honestly, he just wanted the best for Mahoron and bada bing bada boom, everyone left him
I agree with this, but either way someone was going to get hurt and be at least a bit unhappy with that situation. Both sides had good reason not to give in as far as they were concerned. Not exactly a recipe for an immediate happy ending.
The mom probably left on her trip to see if she could gain perspective by stepping away from this issue for a while since she ended up somewhere in the middle herself, not to mention learning about various things that could help. Letting Mahoro go take care of the grandmother's house just helped give the father and daughter some space to keep them from straining their relationship any further in the meantime, I'd say.