Honestly, depending on what brand algae tab your sister uses, the fish food is probably more nutritious than anything TFVG 'cooks'. The higher quality brands are mainly kelp, spirulina, fish, and krill, which you might recognize as being things containing protein and vitamins, not just water and cinnamon. Hell, even the cheap shit brands are mostly wheat and corn. Those are not excellent for fish, but make perfectly good people food.
Not sure which I'd eat if you made me choose at gunpoint, though. Maybe the fish food? Definitely the fish food if whatever TFVG made has the Walden Farms crud in it. Tried it once, found it deeply distressing. I don't even remember where or why I ingested it. Probably for the best.