Before BD for me in MC my W would admit to acting different in front of family and friends then with me. She said she was a different person and could feel more her self. At the time she said she had years of resentment built up towards me, yet she let me believe things were ok.
So you idea of resentment could be a reason for this use of different masks for different people.
Me late 30's W mid 30's T 15, M 10 S4, S7 ILYBNILWY June 2015 In house S July 2015 W rings off Oct 2015 My ring off Feb 2015 Separate houses June 2016