The mother's gone in a downward spiral since she basically got personally told by God that she's a piece of shit, the father doesn't know how to be a parent or delegate responsibility despite being a capable ruler that didn't need his brother's help for all of the previous years, grandma has revealed herself to be a detached bitch with severe favoritism despite having all of the free time in the world to spend with her other granddaughter, and the uncle can't be bothered to give proper advice on being a father despite being what appears to be the only competent parent of the lot.
Our MC is hopefully going to be telling off a whole bunch of people for failing as parents/guardians in upcoming chapters.
As bad as the mother has gotten, I do think much of the blame lies with her husband because if he can't spare any time for his daughter, he certainly doesn't have spare time for his wife during the HONEYMOON period when they both could be trying to get past the wedding mess. It's natural for her to sink into depression after everything happens and he just ignores her like she wasn't waiting during 12+ years of no contact to have a proper (and probably idealized) relationship instead of the mess she's been dumped into.