How to handle terrible in laws?

after abitter split between me & my huband ,both of our family decide to take another chance to stay togather for the shake of our daughter.then onward my in laws started live with us.but i notice my mil trying to make a difference instead of trying to join everything.before that i must tell ,my hisband has ellegal affairs,so there was a biitterness between us.he admitted it also,then after my mil does not ready to accept it.she always complaining that i am making wrong allegations about his son.so at every point she is trying to prove me a liar.like she tells me something when i tell thar in front of the family,she denies it everytime.started crying and behaving like a spychic.so the sympathy always goes to her.she is dominating type of lady.though my fil try to help me in that case,she starts her emotional attyachar.another thing she never helps me ,but in the presence of my husband& fil,she pulls out everything& starts doing everything as if she is doing it everyday.a full to drama at my home,even it happens when ever guests are around.when nobody was there she only sleeps.my husband is not ready to listen any thing because of her drama.no talkings ll work.i have to handle her tactfully,also i want to expose her.& how to take over her.couldnt expect any help from my husband because still we are not compactible.but first i have to handle mil,please help me.still my mil treat her son as a small child,like hiding his every fault& telling him that she trusts her,whoever says whatever.what should i dok