What should i do about my gf mum?

my Girl Friend and her mum own a house , my girl friend should have got it all but her mum refused to sign it over when she turned 18 now they both own it. i work so i pay my way i only stay about 3 nights. But her mum never cleans anything me and my gf do it as her mum says its up to us as she not able ,(which is lies as she can shop for hours a day) she don't work and complains that i pay xbox to much ( i play about hour a day) she also complains that me and my gf spend to much time up in the room and we should come down and spend time with her , but when we do she just watches tv Like soaps and stuff like that , which i hate. and her mum is a Christan and blames my gf for not taking her to church on a sunday and its only a 5 min walk , she took my gf to the side one day and said i should not be going out to the shops on sunday and partying some nights . me and my gf watch supernatural and once again pulled my gf to the side and said that's the work of satan and all this crap. We went on holiday just for a week , when we came back the house was a mess i mean not one dish was washed , the living room was covered in plates and rubbish , she didn't even clean the pets mess ...her words were "you two need to get this house cleaned , im not able and cant live like this" she making our life hard , im trying to get me and my gf are own place but her mum says that she needs my gf there to look after the house so only way we can spend any time together if i stay at hers ...and i seriously don't know what to do . Im 23 and my gf is 19