Never mind, I finally got it. She can't "Serve" Ambrosia, only "Have" Ambrosia, so she makes it for her self only, but can than stop her from eating it, and give it to someone else.
Anyways: Every food is assigned one or more times of day. You can't cook every food at every time of day.
Yes, Ambrosia can't be served. You can only create one portion of Ambrosia.