Lostsoul,
My fiancee is really like your wife,
She would agree with anything anybody says, she can't argue for herself, she just gets beaten to a pulp in arguments.
Now her mother hates me, & my fiancee would listen to anything she says bad about me, what I used to do is ask my fiancee what did she say & then timidly and meekly my fiancee would give me the half truth as not wanting to offend me.
So I'd guess at what it was that was actually said, & then I'd explain my side of it & get her to agree with me (yes my fiancee will argue with me because I'm the only person she isn't shy with).
In this way I'd nip all these things people had said in the bud, she thinks everyone else is wrong now.
What you really needed to do is ask her what she thinks and make her agree with you. Now of course you can't.
I'd love it if my fiancee could make up her own opinion, but she can't, so why shouldn't I fight against all the bad apples? I have more at stake than them! So do you too.
If the problem is she isn't listening to YOU, then you need to try something different, don't tell her anything and agree with everything she says.
Either-way get her to move back in and take it from there.