Baby only drinks 2oz at a time?

Our 4.5 month old recently started a new habit of taking 2 oz of milk at a time. We make 5oz bottles from frozen breastmilk, thaw it and offer it after it’s been warmed. She gladly accepts the bottle, drinks two ounces ferociously then pushes her bottle away. She WILL NOT drink more than 2 oz at a time, maybe 3oz on a good day. This leads to offering the rest of her bottle every half hour until it’s finished or ready to be tossed, so a new one is made.

She is not gaining weight as quickly as when she was younger. I do have high lipase; yet she doesn’t make faces or technically “reject” the bottle. It just takes a little bit of effort and patience.

I’m now at the point of trying scalded milk, apprehensively (I don’t want to overscald).

Has anyone else had this experience? If so, how did you manage it?

**ETA: she is drinking 25-29ish oz a day, and teething.