worried mommy of three.

I'm a mommy but only to my four legged babies until we have a baby of our own (TTC 15 months) 

As I've told many people my cat thinks she is a dog, and acts as though she is one, all but a few things. That being said the way I have found most beneficial for my three fur babies feeding wise is to always just leave food and water out, that way they can eat when they are hungry. (It's helped them all maintain a healthy weight and keeps my oldest from having belly aches). So they ALWAYS have food, but my cat has decided she is going to eat the same thing her brothers eat, even though it's dog food. She only eats her food if I put her in the bedroom while we are gone (that's where her food is) and she can't get to the dog food. I'm worried with her eating dog food she isn't getting the nutrition she needs. Anyone have any clue?