Helping my mom or not

Ok so I'm really confused on what to do and I really need you guys help on what I should do ?  My step dad is leaving in two weeks for deployment and my mom calls me every day demanding that I need to move in w her while he's gone (10-11 months ) but lately she changed it to just a first month cuz I kept saying no to her. She wants me there to take care of the house and my sisters. But here's the thing she left me when I was 12 with my 6 and 4 year old sisters w my grandma who was on drugs ("prescription med ") which made me no choice but to do everything for the kids til when I turned 16 she took us in. I left home when I was 19 cuz I was still doing everything and paying her the rent and etc . now I'm married. she says there's a lot to do and my sisters have " no time" to help her and they don't know how to (17,15and 6 yr old) which makes me so mad that they are getting Loyal treatment and I have to go there to do their chores for a month. I'm not saying that I'll never visit them or anything. I'll stay and love to help for a week or so but a whole month? Husband and I go there at least twice a month for few days and idk why that's not enough for her. Yes it is hours away from where I live and we share one car and he works 6 days a week. No I don't have kids or job so I am free but so selfish of her to tell me what to do cuz her kids can't do the dishes. Am I wrong? Should I stay for a month? Im thinking of telling her I can stay for a week every month but afraid that she gonna get mad. In the past she kept me away from seeing my sisters for months because I didn't "listen " to her which I hate. I love my sisters and I seriously do not want to miss the holidays w them so please help?