I wonder if DD always having been put first,still sees it as her right to still be put first.
I see nothing wrong in a couple having 'us' time and quite often look after a child who is not my biological GD,to give mum a single parent some breathing space when needed.
I never left my children we always went as a family,but neither GP where willing or able to help,after 26 years my marriage collapsed due to ex having worked 24/7 and no longer having anything in common.
different situation now DGD lived with myself and new partner after the death of my daughter,new partner arrived first and we all had to shake down and make it work,DGD went to spend a week every so often with my ex and his new partner,and was happy to do so,she is confident and happy to embrace all things new.
I have read that it takes a village to raise a child.
I appreciate every one has different views and circumstances.
The difference in confidence between my GD and my son and daughter is very difference.