Did you get her from a pet store such as petsmart/petco? Most of the time they don't know what size to properly feed their snakes, or they just go the cheap route such as pinkies and only one a week. Don't worry though, if you feed her right, and often for a while, then slow it down to a weekly schedule, she'll do just fine. For reference:
Eva when I first got her


Notice she was also VERY skinny. This was right at the end of July.

Now, over 6 months later she's nice a plump. LOL:



Btw, yours is really cute.