Is Lei ha chiesto per il cibo actually grammatically wrong?
Lei ha chiesto per il cibo
"Ask for" = "chiedere". http://www.wordreference.com/enit/ask%20for and http://www.wordreference.com/enit/ask
You won't find any "per" in those pages. ;)
Technically yes - you wouldn't find that written anywhere, but it is sometimes used when colloquially speaking. It's like saying "She asked about the food".