Weird sentence. Perhaps "... wants her own personal food" is a more normal English expression of the idea, though you'd probably have to use 'propre' in there somewhere.
In French, if you say "la reine veut sa propre nourriture personnelle" it sounds redundant (propre and personnelle meaning exactly the same thing).
why is "son repas personnel" incorrect ?
Because Duo expects a direct translation: food = nourriture.
But I will repeat myself once again: we don't use "nourriture" as often as Anglos use "food" and really another word would be found in French: repas, aliments would do a better job.