Feeding my two month old rice cereal her G.I. doctor recommendation

Sarah • 27. Married. My son was born 2/22/16 and his little sister 7/5/17

OK so this is going to be short and sweet basically my daughter has severe food allergies her G.I. doctor has put her on prescription formula and she also has severe reflux so she is on Zantac and the doctor wants is adding a entire tablespoon of rice cereal to every bottle she was doing OK for a while, last night she had a very scary episode of vomiting and choking on it my guess is that this was even harder for her considering the consistency of her bottles! But another thought I was having was maybe she's eating too much? I try to feed her on-demand but perhaps she is mistaking a tummyache for hunger she takes 3 ounces of formula mixed with a tablespoon of rice cereal every three hours is this too much should I try and make her hold off for longer? Just wondering if I'm overfeeding her and that's why the reflux is getting so bad or if this is just part of reflux 3 ounces alone would be fine for her age but considering I'm also adding a tablespoon of rice cereal I thought she should be full for longer? Calling her G.I. on Monday but looking for some opinions now..

I also wanted to add last night she was vomiting profusely and was choking we had to call 911 thankfully by the time they got here she was crying but it was terrifying they recommended we call the pediatrician on-call I explained to him that I thought she was choking due to the fact that her formula was too thick he was very stern with me and said I should continue adding the cereal and that it was supposed to help with reflux not to make any changes until I talk to her pediatric G.I. who put her on this regimen... naturally this had to happen on a weekend so from here on out I just don't know what to do until I can contact her again!