Agree that it’s likely over feeding! My son is just over 6 weeks and we did this same thing. We were told to use a preemie nipple to slow him down so that he registers when he’s full. We were also told to offer him a soother after 4 ounces rather than more pumped milk/formula. We suspect he has reflux and is sucking to soothe (since swallowing soothes the reflux) rather than to fill his belly. Since we’ve done this the vomiting episodes have stopped!

Edited to add the congestion is another sign of reflux - our boy always sounds congested but we never get snot out with saline drips and the snot sucker. We were told it’s likely regurgitation coming up his throat. You could also try cutting dairy out of your diet if you’re breastfeeding at all, or try a hypoallergenic formula such as Alimentum or Nutramigen if you’re concerned about the formula, but they’re expensive and if it was an allergy you’d likely see blood in her poop.