Perhaps the author is implying that Heath is more or less identical to a human in terms of what foods are beneficial or harmful to her, with the sole differences being in things like digestive efficiency and how much a harmful thing can actually harm her (i.e. something that could kill an ordinary human would just give her a severe stomachache and/or diarrhea).A twist that seems not to have been explored is the possibility that things that Heath can eat might be harmful to Lily.