Both of my boys had AR. I remember with my oldest that the Zantac did not work and I think he was put on Prevacid or Prilosec. We also elevated after feeding and added rice cereal to his bottles.
Both my guys also had the gagging. My oldest went to a speech therapist to learn how to chew his food... It took about 8 appointments and he finally stopped gagging and vomiting his food. I lived in DE at the time and all of the cost for those appointments were covered by the state and our health insurance, so there was no out of pocket expense to our family, which was very nice.
You can contact me through Mamasource anytime if you have any questions. My best advice is to watch out for acidic foods, and remind her to take small bites and to chew her food at meal time. Also, do not hesitate to go back to your pediatrician again and again until you feel she is feeling some relief from the meds.
The good thing is that it goes away about the time they start walking, which for me was around 10 1/2 months for both boys. Hopefully your daughter starts walking soon.
FYI - if you have one child with AR, you will likely have another with it...
Good Luck