We live with my in laws to help take care of his father but my mother in law doesn't respect me as far as my stepdaughter goes.she doesn't allow any form of discipline for a 6 yr old,even including taking toys away.she also fixes boredom and temper tantrums with food and I strongly disagree.she already weighs 97 lbs at 6 yrs old and I fear for her health.
What I would do is have a discussion with your husband. Agree as a team how you will handle disciplinary issues. Then have a meeting with his mother, without the child present. Have him explain the rules. She doesn't have to respect them or like them. You two are parenting the child, and she needs to abide by your team decision. Tell your husband he needs to be strong on this issue for the sake of his daughter. She is the priority.
I completely agree, where is your husband in all of this? In laws especially the parents of the husband are notorious for scrutinising your parenting techniques however she needs to back off. when you married her son you made a commitment to him and his daughter and also to his mother, you owe it to her to be respectful but at the same time the child comes first she needs to accept that and if she cant then perhaps you need to think about finding alternative care for your husbands father and giving each other breathing space. It can be stressful when a family memeber is ill so it is even more imperative that everyone else stays healthy. You need to talk to your husband get him on bored and if she still wont listen go to your family doctor get him to explain to your over bearing mother in law that she is hurting her grand daughter with love.