I prefer she get her vitamins and minerals from natural sources.
I agree. If I could, I would feed him a whole garden

(Did so before when I had pets and lived in a place where having a garden or foraging was possible. My birds also loved the clover and dandelion and picking them was an easy thing, not much to think about.)
Here, I feed my dragon vegetables (including greens) from the supermarket (organic), plus his beloved golliwog of which another soccerball-large specimen, still on the windowsill, awaits the confrontation with dragon teeth
If possible, vitamins and minerals from natural sources are really to be preferred, as (also) for humans, the body usually relies on other micronutritients found in that food to make use of those vitamins and minerals - as they usually occur together, the body has adapted to process them this way together. Same for me: I prefer getting my vitamins and minerals from "real food", instead of from powder shakes, vitamins and such (also as a vegetarian eating an almost vegan diet).