Please help me, I'm worried about my parents?

Ok so my mom has always been a little overweight but recently its gotten a little worse. She sits in front of the tv ALL THE TIME when she's not running errands and whatnot. About 2 months ago she started getting this cough and it still hasn't gone away. At first the doctor said it was allergies (she has terrible allergies) but her allergy medicine wasnt helping. Then they said bronchitis but the z-pack didn't work. Her cough is getting on my nerves. But not only that, her laziness is really pissing me off. I try and hint her to go do exercise but she always replies with something like "I don't feel well" or "I'm too tired". I'm honestly starting to get seriously pissed off. She's 55 and my dad is away on work a lot and I just want her to get into shape. Plus she does not eat that healthily, she always snacks on food. I honestly think that exercise would help get rid of her cough once and for all. Plus she always complains about how she's tired, and thats clearly a consequence of never exercising. I'm honestly worried about her health but don't know how to get her off her ******* ***!