Get solid blue party bags and then tie a small, yellow helium balloon to them, so the look like a loot drop. (A friend did that.)
Cupcakes with white icing and a red cross, so they look like a med kit.
Any blue juice, maybe in small mason jars, for slurp juice/ chug jug.
I don't know how many kids or tables, but you could name areas for cake, eating, etc after places on the map. The bathroom could be Flush Factory. Tables could be in Tomato Town. Presents to be put in Tilted Towers (or Junk Junction LOL).
I think fortnite is a video game and she means a fortnite themed party. But I wouldn't bet my life on it because I got very confused when googling. Soccer came up too?