I don't think she eats enough

I have a 6 year old female cat that I worry that she doesn't eat enough. When I give her a dish of food whether wet or dry she eats very little. She may just turn her body around away from it, she may try to bury it like she does after she's done in the litter box or she just may leave. I have another female cat I would give the same food to and she gobbles it up and alot of times try to get my other cats food. Beings that my one cat I don't believe eats enough, she and my other female cat are around the same weight how can that be? I worry about her not eating enough and wonder if there is something wrong, but she has been doing this for a while now. She seems very timid and will move away and let the other cat eat her food. My other girl cat is a calico and has a little tud to her she hisses and growls easily could my other cat be threatened or that's just the way she is.

 I need to know why she doesn't eat much is she OK?

Some cats are snackers and some cats are gobblers.

Your girl might be a snacker and only wants small amounts of food frequently.

How often do you feed your kitties? You might want to give your picky kitty treats a couple of times a day, and it can just be piece of their normal kibble too, not a treat treat.

Also if you Calico growls and hisses while eating separate their food farther apart. The Calico is threatened by the other kitty and being food aggressive. If she's just growling and hissing all the time then she's just displaying typically "Tortie-tude".

As long as she is at a healthy weight I wouldn't worry though. I have yet to find a cat that doesn't eat enough, Most of the time they eat to much...

I have encountered and dealt with kitties who starve themselves but they wouldn't even eat a bite or two of kibble. 

She might just have a slower metabolism too, or a lot less activity level so she doesn't need as many calories.

But as long as she's not underweight I don't think you need to stress out.