I’m devoted to my DC, I also work 40 hours a week because my family needs that income to survive. My DH also works 40 hours a week. Unfortunately my hours are not around school hours and so my DC are cared for by nursery and a childminder. I also do the housework, DH does the cooking and we share other chores between us.
DIL sounds like a lazy, entitled brat who has had the luxury of living off a corporate wage for a long time. Of course her contribution as a SAHP has been invaluable, but the children are at school and circumstances have changed. She needs to step up and show her devotion to her children by getting a job to support them.
People who live off their parents when they are fully functioning adults make me sick, I see it all too often - lazy and entitled adults who are happy to take money from their parents, based on the fact their parents are worried sick about them and want to help. It’s emotional abuse and extorting money through insincere means.
The SAHP role is always going to cause a divide in opinion, in this case it’s simply that having that role no longer works for the family. The DH will need to take on a more honest share of the household tasks to assist the DIL to be able to work. If being a SAHP is work then this is simply a changing of jobs, something which many of us have to do whether it’s what we’d prefer to do or not.
Give them a deadline, and stop supporting them. If it causes issues in their marriage then it really isn’t your responsibility. You sound very kind.