Your vet doesn't sound like a good BP vet. I would see someone else if you can. I had to give oral meds for sniffles and it sucked, but I did find that lip peeling made it much easier. Don't expect her to eat for the entirety of oral meds. She will be irked and handling her for medication will probably just make her regurgitate anyway. I think if you've only had her over a month, you may just want to soak her and not stress her out by taking her to the vet. She may be absolutely absorbing all the food she can when she eats. Personally, I would finish the rounds of meds (unless they seem to be making her worse) and find another Doctor. This one doesn't know the barest basics of BPs and that is a terrible sign. I've known many vets in my area and gotten local reviews and the animals that did best during medical issues went to Doctors that bothered to (insert sarcasm here please) wikipedia the species they were about to treat. I know it's a stressful job and they often have to see animals they may know very little about. Vet schools don't cover things like tarantulas and exotic bird species in many cases. HOWEVER, balls, boas and corns are pretty common snake pets and the doc really ought to know some minimal amount about them before they treat them. My vet never blinked at "poops every three weeks" about my kids and had a pretty good idea of how much weight a growing snake ought to be gaining. She would occasionally ask a question to confirm 'general behavior' because she knew I've owned them for years and was willing to admit she didn't know everything about them, but she also had a very good understanding of overall herp and overall BP anatomy and basic requirements! A vet doesn't need to know ever single thing about your animal to treat them, but they really do need to know SOMEthing!
I hope this doesn't sound rude or condescending, I just would hate for you and your new girl to go through all this stress for something that might resolve itself, OR be fixed by going to a Doc who knows reptiles!
Also, i forgot to say earlier, try not to be stressed. Your snake will be wigging out and upset, but the calmer you are even if you think you have no idea what you are doing, the better each dosing will go! All that snakes really need is for the medicine to not go down the breathing tube and to be gentle enough not to chip teeth. If you move carefully and decisively, it will be much easier for everyone! Good luck and try not to stress about it.