Hi Y.,
My advice is, if she is not in pain, don't give her the Zantac. My son was prescribed Zantac at two months old becasue he gulped constantly during feedings (breast fed). Doc said, "must be acid reflux" and prescribed Zantac. After about a month on the Zantac, there was no difference in his eating habits. I did some research and found out that the Zantac does nothing to actually control the acid reflux, all it does is neutralize the acid so that the reflux doesn't cause the baby any pain. It has no effect on the muscles or mechanics of the esophagus, so it does NOT suppress the reflux action. Since my son was not in any pain to begin with, I stopped the Zantac (oh, it tasted HORRIBLE anyway..worse than any medicine I have ever had). He is now a happy and healthy two year old. For some reason, acid reflux is the "in" diagnosis right now, as I know so many babies over the past few years who have been on heartburn meds. In my son's case, I don't think he ever had acid reflux either.
As for the eating... maybe try moving up a stage in the nipple you are using. If she is having to suck to hard to get the liquid out, maybe she loses interest. And, make sure you always offer the bottle first, before any solid foods, at each feeding. She should still be getting all her nutrition form breast milk or formula. Baby food and cereal is for training, not nutrition.