need advice please

My father in law passed away in December right before Christmas . He was very sick on dyalasis and couldn't really see anymore. He had a heart attack and they couldn't revive him . After his funeral and everything we came home from south Texas and my mother in law tells my fiancé I can't do this on my own . I can't pay the bills blah blah blah . So he tells me that we might have to let her move in with us . We lived in a one bedroom apartment so my fiancé decided to ask my aunt if we could rent out her house bc of everything that's been going on and she said  yes so we signed a contract for a year . 3 months pass and we are all living together but my mother in law starts moving on already . She has 2 boyfriends and I guess can't decide which one she wants . She finally decides on one of them and told my fiance I don't want to pay the rent here anymore and my boyfriend asked me to move in with him . My fiancé is a momma boy I swear bc he tells her okay and decides that me and him and our 3 dogs have to move outta here too basically screwing over my aunt and our agreement . We are moving into a rv soon . It hasn't even been a year yet and my mother in law is totally moved on and my fiancé and his siblings refuse to care . It's ao frustrating and idk what to do . Sometimes I think about leaving him bc he hasn't been the same since his dad passed but refuses to get help or even admit he needs it . Am I wrong to be so angry with my mother in law and finace ?