try asking your mum to cook in olive oil, it has less saturated fats in it than veggie oil. or try to get her to steam vegetables rather than frying them. you can also drain out any excess oil that gathers in your plate, that way you don't have to ask her to change her cooking. why don't you try having your own breakfast and lunch and then you only have to eat your mum's dinner. or at dinner time, eat more of the salad and less of the curry, that way you are still eating the same amount but just of a different thing. indian cooking is very bad not only for weight but for other things too, like cholestrol levels.
also remember that energy in has to be less than energy out, so there won't be much effect on you if you eat excessively and exercise. if you think you eat too much then maybe try drinking lots of water before dinner time, it might make you feel more full.