So why insinuate her in laws were to to blame? She wasn’t trapped. Her mother was free to help. Her husband was.
You say he should have done more. You said “Harry said he tried to ask too but they said no.”
So he choose to do nothing then because they allegedly said no?
And although she may have felt trapped as you put it, she wasn’t. That has been established.
If she was too unwell to seek her own help then I don’t believe they were not allowed to seek help for her.
Help could have been arranged when she went overseas. Why didn’t they do that?
Imagine letting the woman you love flounder. That is shameful.