is she sick ?

Ok so just want opinions cause i have others kids and not sure if my little one is sick or not. I woke up (6.30am) to my 8 year old telling me the baby vomited in the cot. she said she was crying but didnt hear her vomit. I didnt hear any of it either must have been real tired. Anyway, i went in there and she had vomited in cot and was crying (not hysterically). I am not sure if shes screamed and screamed till she vomited (has never happened but she has gagged) or whether she has a virus. She seems ok and has good colour and is drinking some water i put in her bottle. Just want opinions on what you guys think it could have been because i am worried it may spread around house