If she is faffing about then she might be taking more air in, and the increased wind can make them sickly.
Obviously reflux can do things like this, but it usually presents at about 2 months, and has a big affect on sleep etc.
I assume you haven't changed formula or started solids?
My DS2 has cows milk protein issues, but again they present early in formula fed babies. He also vomited his whole feed up after about 45mins, and diarrhoea after every feed.