Why isn't she interested in eating?

Monday through Friday I watch my (technically second cousin but I consider her my neice) neice from about 7am to about 3pm. When she gets here we both usually end up falling back to sleep on the couch until about 9-ish. After we get up, I changer her diaper, and change her out of her jammies. Now, since she is with me for a good chunk of the day, I feed her 2 meals, or a late breakfast and a snack. Usually I just put the food in a bowl because we are trying to get her to feed her self.( Gold fish crackers, cut up pancakes etc.).

But, for the past few days I havenoticed that she doesn't want to eat much. I heated up a left-over hamburger and cut it up for her..she ate a few bites of it..then proceeded to cough it up because I forgot that hamburgers get hard when they are re-heated. So I tossed it out. Then, I heated up some mashed potatos. She took 2 bites and that was it. Then, I made her a pancake. I cut it up and put it in her bowl. She ate a few bites, then just sorta left it there.

When my aunt comes to get her in the afternoon, I tell her how much/what she ate. Then the next day (if the baby hasn't eaten much) she tells me that Layla ate a lot more then usual that night.

Why is it that sometimes, Layla just doesn't seem interested in eating? She just turned one if it matters.

sorry so long