I feed mine every 7 days until they get to be a couple years old. Then they move to every 10 days, and actually my big creamsicle female only gets fed every 14 days and is a very healthy weight. I'd say 8-9 days is fine for an 8 month old, but it definitely couldn't hurt to move her to every 7 instead. Most corns always act hungry no matter how much you feed them, so if she seems to be a healthy weight I'm sure she's fine