I don't really know what's going on or if there are MH issues or what. But short-term, I would suggest she and her husband split the kids up. She takes one and he takes the other. Maybe same-sex? Or maybe she takes the more tractable child? And she should spend some quality time w/ the one child doing activities the mother finds fun, but engaging the child, too. So she can enjoy the child as part of a normal, productive, stress-free day or wknd, rather than being mentally drained by two brats, tag-teaming her and reminding her of how fulfilling her life has become.
Then the next wknd or whatever, she and her husband switch off.
Or if money isn't an issue, why not encourage her to take a trip somewhere alone or w/ friends to give her a chance to miss her kids.
IDK if you're implying this woman is abusive to the kids or just lazy or just clueless or what.
If the kids are both in school what does she do all day?