Fast metabolism catches up to you?

My stepmom eats bags of chips fries at almost evey meal patatoes with tons of er baked onto them and i have yet to see her eat something that is good for her if she has a choice is this going to catch up to her? her eating habits made me severly over weight and before my farther was with her i was in shape and now im working on losing weight but does this catch up with those kind of people? and is she unhealthy inside??