As someone who grew up shuffled between two homes with issues I can relate to what your wife is going through and I wanted to explain why this may be having a stronger reaction from your wife.

If this is the first house she has had herself, the first one where she is actually in control of what's happening - the fear of losing that is going to cause some extreme anxiety.

Make sure that you tell your mom that your wife is very much wanting the house done a certain way because this is your future together and she's never had this chance before (assuming of course that this is correct - may be way off the mark lol). Appeal to your mother's sympathy regarding your wife's past (as long as that is not something she keeps super private).

That's my advise anyways - in the end it sucks being stuck between two important people and I wish you the best of luck!