To help cool the body and soothe a sore throat caused by inflammation or coughing (as opposed to postnasal drip; for that, you consume starch to sop it up). Sorbet, Italian ice, shaved ice, or something along those lines would usually be better, but that depends on the symptoms (if their stomach is in good shape, then ice cream can be better). So, I'm assuming that Fiona has no digestive symptoms but the inside of her throat feels like it's burning.
Overall, what's best to do depends on the illness and its symptoms. (And obviously, a patient suffering from injuries is another matter.)
Personally, I've always found the Japanese trope of feeding a sick person pork to be the craziest and dumbest thing: red meat and its fat are both infamously difficult to digest — not what anyone with a lick of sense would call good for a patient suffering from an illness. (I don't think the mangaka/authors are bothering to think about it, usually. And, to be fair, works which go into actual traditional Japanese treatments usually stick with congee — which is really a type of rice gruel/watered-down porridge — or udon, both of which make a lot of sense. Often supplementing it with easy-to-digest vegetables. Common sense, really. Which leaves me wondering where the pork nonsense came from. Even fish or mushrooms would be better — not that I'd recommend either for the task.)
The best things to feed a sick person are grains/starches, clear liquids, and lean poultry (never something like duck or goose) — thus why Westerners usually feed patients a soup consisting of chicken or turkey broth, easy-to-digest vegetables (carrots, onions, etc.), a starch (usually rice, noodles, barley, or potatoes — in that order), and, sometimes, small amounts of the bird's white meat. …Unless it's a stomach aliment, in which case simple grains are the only way to go.