By all means dismiss my opinion, but MN is full of stories of awful inlaws.
The Hen do is nothing to do with the grooms family, yet his family are scandalised by her choices and she writes that they might blame her.
Her SIL insults her at every opportunity.
Does the OP's husband have any opinion on his SIL rudeness? Or does he tell her she is sensitive, or pretend not to hear?
Are the rest of the family witnessing the rudeness?
If his family are as described the OP would do well to pause and think about what she is marrying into.
It is utterly naive to imagine marrying into a family of strife will not impact on the marriage.
OP is afraid of upsetting her inlaws so assuming she is going to be able to impose boundaries might not be possible.
If her intended is cowed by them, I think she may find that she has a long marriage ahead of her.
In the real world it would indeed put some women off getting further involved with someone.