your friend's top priority now is to 'save' her parents. now the question is "who will save her parents?". if she D him, she will be the saviour (coz she sets him free). if she stay married, maybe 50/50.
husband; no blood ties.
parents; blood ties.
why don't stay married (for the time being) and think of a way to pass the mess (liability) back to him?
since he is a goner, stay on. understand?
with him 'binded' (contractually) there's always an opportunity (to pass the mess back to him).
