Having the support from those who live with you is important to help you reach your fitness goal. I believe education is a big step in helping her making better choices when preparing the meals. Try educating and helping her understand why you want to cook healthier meals. You can ask if she would be willing to commit to at least one or two healthy meals per week. And the other times, just practice portion control to make sure you keep your calories to a minimum. Once she sees you reaching your goals, she may change her ways because of your example.