Hey there Tina!
I'm only a couple of years younger than you and at my heaviest i was 259lbs and i am now 240lbs and i had the exact same problem with you when it comes to living at home, my solution though was to buy my own food, put my name on it, dont eat any of the familys food and they wont eat mine. Sounds petty but it works as you think to yourself that aint mine i cant have that and you are just left with what you have bought. Although obviously just stick to buying food that is good for you.
Also when it comes to water, some people dont like it, i for one can not stand it. You dont have to drink plain water if you dont like it you are able to add some sugar free dulutable juice to give it that bit of flavour.
Another handy hint is to always have chopped vegetables and fruit to hand if you feel peckish and always, always carry a bottle around with you with your fluids in and drink throughout the day.
Get yourself in the mind set that you can do this and you know you can! You will show your family you dont need them to cook your favourite meals for you and you can do it on your own! If you want a buddy im happy to be there

just send me a private message or something if you like.
Oh, and Good Luck sweetie