How can I learn to atleast pretend to like my futur mother-in-law?

[Emma]

I'm going to give a brief story of my bf's family. His mother has 6 children, she has one kid with a man no one even knows. 2 kids with another man that was an alcoholic. and then 3 with a man who was married to someone else (which is my bfs father) and now shes with another man that shes been with for probably about 15 years, hes a very very religious man and all of a sudden she became totally obsessed with god. my bf's brother is in jail for robbing a bank, she allowed her 16 year old daughter to drive with out a lisence and go to bars, 4 years ago when i caught my bf taking drugs and i called her her reply was "oh no honey he's not on drugs, trust me i would know" when in reality she doesnt even no anything about him, its like she lives on another planet. she's never taught her kids how to be dicipline, responsibility or punishment. she never cooks or cleans, to the point i dont even want to go there bcuz it smells.(and she doesnt even work, so she has alot of time to clean) when my bf has a disagreement with someone her resolution is "oh their just jealous of you". she never looks at both sides of the situation she atomatically has to defend her kids, even if they were in the wrong. it makes me sometimes angry with my bf bcuz when we fight and he always acts like he's right, he'll never look at it from my side, i feel like its his mothers fault for not teaching him to comprimise instead of always defending his side. and every time she speaks she always gives out false infortmation, example.. my bf asked her if cancer was genetic and she said "oh no of course not honey" it rly gets on my nerves cuz i feel like she makes him stupid. can anyone give me some advice of what i should do. do you think its a bad idea if i tell her exactly how i feel? (i dont rly know how with out calling her a bad mother)