Mom , grandma (my moms mom) and moms fiancé

Okay so my mother bought a house last April. My grandma wanted to move in so bad . My moms fiancé was in jail around the time my mom bought the house. So we moved in my grandma paid half on all bills , she cooked (still cooks) she cleans , she walks the dog (which is my moms) she feed the dog she buys everything the dog owns. Basically you might as well say she’s the owner of the dog . So my moms fiancé comes home he moves in now they all split up the mortgage and utilities . My grandma stopped liking him for a few things . One was everytime she cooks (she cooks every Sunday and about ice during the week) he never eats her food. But when he cook he sit at the table and eat.. also he be so quick to use my moms car sometimes knowing my grandma has to go somewhere. Then there’s times when our family is over and he either leaves or be on his phone. There was a time my grandma made fish for fish sandwiches . She had set it up like a fish buffet , she had lettuce cheese etc and they came home and just left and went to the mall. She felt unappreciated because the least they could’ve done was eat then leave . She doesn’t like him at all so she will find anything to be mad at home about but my question is .. who’s wrong ? Is my grandma over thinking it ?? Is my grandma wrong for moving in because she had her own place, she’s very active to be 64yrs old . She has so type of health or mental problems . This is a fresh relationship with my mom with her fiancé so they should be able to have a house by their selves or is my moms fiancé wrong for everything he is doing ? AND I WOULD ALSO LIKE TO ADD she had told me he has been making comments about her leaving and never coming back (moving out)