I have a problem with my dog?

She is a 5 1/2 year old beagle. So my parents aren't quite the doggie lovers. Ever since we've had her, when she's outside, she would scratch scratch scratch, bark bark bark, to be let in. Now she knows just to scratch a little to be let in. The thing is, I have school and work, so she's usually pushed onto my parents who have a hell of a time with her. We have a cat too, so she eats the cat food when she knows shes not supposed to, she eats the cat poop (ew?), and very seldom does she use the bathroom on the carpet, but that's gotta stop too. I feel bad for my parents, because when I'm here, I know how to control her, I just keep her in my room with me, and never let her be by herself in the kitchen. But when she's here with my mom or dad, she does all these bad things, and I dont know what to do. We have a kennel. She's overweight, so were feeding her less and healthy food, been like this for months, it what the vet recommended, so don't tell me she's starving because I feed her. Now some real help please, I could really use some help. Thanks.