M.G.
My child has not had that specific problem. But, my 4mo old just got over stomach flu. He had it REALLY bad and was vomiting 4-5 times a day, and every diaper was SUPER watery poop. He had stomach flu for 1.5 weeks, got better for 4 days, and then it came back for another week. We went to ER 4 times during this time period becaseu he was unable to hold any food down PLUS he was having diaherria. He also started to show some VERY EARLY signs of dehydration.
SO....I Doubt your daughter has stomach flu...but it COULD be coming on. So....i would just watch her. She is probably totally fine, but I would buy some pedialyte and after she vomits, give her half pedialyte and half breast milk at her next feeding. Pedialyte will replace any electrolytes that she may have lost. Vomiting once a day is not going to cause a serious loss in electrolytes, but giving her pedialyte will reassure you that any electrolytes that may have been lost will be replaced.
So...just watch her. I doubt it is stomach flu...but supplementing with pedialyte may ease some of your concerns about dehydration. Just an Fyi....my son NEVER had a fever and was SUPER HAPPY when he had stomach flu. So.....in my oppinion fever/temperment is not always a good indicator as far as health goes.