7 y/o vomit and diarrhea 10 days ago then stopped. 2 days ago - much diarrhea and yellow bright vomit - 3 times at nighttime. pain around belly button, feels terrible. gastroenteritis for this long?

No: It sounds more serious than viral gastroenteritis. There is bacterial gastroenteritis caused, say, by salmonella, which may last that long. I'd definitely take her to the doctor at this time.

Unlikely: It would be unlikely for your child to be completely better for so long and then get sick again with the same illness. This second illness is probably caused either by a different infection or something else.