They don't usually recur that often, but a couple of times a season/year is not unheard of or unreasonable. Some strains and just like that, and some kids seem to catch all the various strains one particular year, then might not get it at all for following years. It's also common for it to go up and down from day to day, especially if this is one of the first times she has had this bug in her life. As long as blood tests are fine, I'd say you are in the clear. Her telling you today that she wants to throw up may not actually mean that she has to... she may be a little gun shy after the virus, or might have kind-of enjoyed the attention she got from you when sick. A 4-year old is a complicated little being! They "get" more than we think they do, but they are still babies in many ways.
However, I also agree with others' suggestions about watching what she is eating and seeing if there are patterns there. Did she push it yesterday after feeling better and eat a lot of dairy or meat, and other things that are hard to digest? Go easy on the diet for the next couple of days, and let her tell you what she is ready for if at all possible. She will probably be very hungry, but her body might not be ready for a lot of food all at once. Honestly, those stupid "24 hour" bugs suck the life out of an entire family. I HATE them! I hope she is 100% soon.