Mokkah was not a big eater when I first got him, and it took ages for me to get weight on him---now no one can get between him and his food, although there are some times where he leaves the chicken necks behind. He does have a much more sensitive tummy than Hailey, and grazes on grass like a goat.
I do notice that both my greys tend to eat less when it's hot. I wouldn't worry too much, as long as she's not dropping weight.