It's possible that its a bug and she's not quite recovered. It's only a short amount so time so far.
It's also possible it's reflux. When my DS was a baby he projectile vomited very single feed and spent his evenings screaming, it was horrendous. He was on gaviscon by 8 weeks and on ranitidine not long after. He's still on it now at 23 months and has a cows milk protein allergy to go with it.
I would see how it goes. Things you can do to help reflux is wind regularly throughout a feed, put towels under the head of the mattress to tilt it and keep upright 20 minutes after a feed. Possetting wouldn't worry me, it's normal, continual vomiting is different, especially if she's uncomfortable with it.
My DS always put on weight (not sure how), some GPs seem to use this as a measure of how bad the reflux is, which is bollocks when your baby is screaming in pain.
Sometimes also after having a bug your gut can become temporarily intolerant to milk as it irritates, which generally settles down. See how things go, if it doesn't settle then I would go back to the GP next week. As long as she's not dehydrated in the mean while, plenty of wet nappies, fontanelle not sunken, skin not dry.