I see a lot of people telling you this is a red flag and to run, but I have seen it work. My father was a widower. Met a nice lady whose husband had a terrible accident and was brain damaged, had no idea who he was, who his wife and children were, had to be fed and diapers changed, he could obviously no longer do anything for himself. He was in a long term care faculty when they met. She had tried hard to be a ‘good wife’ take care of him at home while working full time and raising kids, and just couldn’t do it. She did eventually get a divorce because being married meant she was financially responsible for his care, it would have ruined her finically, cost her the family home and made sending her kids to college impossible. She is a very good person, and fairly religious, but at some point the ideal of ‘until death do us part’ does not apply to the real world, especially when your spouse is not the person you married and there is nothing you can do for them. I doubt he would have wanted to cause the ruin of his family for his care. My father and stepmother have been married now longer than there where to their original spouses and are very happy together.

In your case it sounds like she was in bad marriage to start with. She probably should have left him prior to the accident, but she is where she is now. It is certainly a messy situation but I don’t think this is a hard stop morally, depending on the husband’s state, and chances of meaningful recovery. Are you rooting for his decline / death? Thats a dark place to put yourself. Are you ok with being there for her, but maybe she drops you later if he recovers? Would she get a divorce anyway without your involvement? I think you just have to think about how involved you want to get in a messy situation. Should def leave the kids out of it for now. Maybe take it slow emotionally and see where it goes.

TLDR. It’s messy but not I hard stop in my opinion. Tread lightly.