Relationship would be related to Fi (though I don't know any Fi types who would behave precisely in the manner in which you're describing for the sole purpose of preserving the relationship), mood would be related to Fe.
Being non-confrontational could be related to weak/unvalued Se. Also, Te dominants have a Fe Role, so sometimes they worry too much about not upsetting people. (There are plenty of logical types who behaving illogically, btw.
It's a matter of whether you're using the Socionics definition or the English definition of the word "logic".)
Anyways, people of many types could behave the way you described for a variety of reasons.
I'm a bit confused about your mil though... you describe her as both controlling/overbearing and non-confrontational... I'm having a hard time imagining the combination.