For now to help with gastrointestinal upset and reflux you can give either:
1) Pepcid ac (famotidine) at a dose of one 10mg tablet per 20 to 40 pounds of body weight every 12 hours (2 of the 10mg tabs every 12 hours for a 55 pound pup)
2) Prilosec (omeprazole) at a dose of one 20mg tablet per 40 to 80 pounds of body weight every 24 hours
These are acid reducers and should help her feel more comfortable. They are quite safe and should be used for several days.
I would offer a bland diet mix of 1/3 boiled, minced, white, skinless chicken or boiled, lean hamburger, all fats drained off the meat after cooking, and 2/3 boiled, plain, white rice, mashed potatoes or pasta mixed with some low salt chicken or beef broth to make it easy to lap up and swallow as well as increase her fluid intake.
Probiotics such as Fortiflora, Proviable, or Benebac can be added to the bland diet mix to help replace appropriate bacteria.
If things go well and she eats and seems more comfortable feed her the bland diet for 2 to 3 days then slowly start to mix back in her regular food, a little more at each meal. It should take about 5 to 7 days to slowly convert her back to her regular diet.
If she begins to vomit, runs a fever (more than 103F rectally), or has a tense painful belly then she is not a candidate for home therapy and must see a veterinarian for an examination, diagnostics, injectable anti-nausea drugs intravenous fluids and supportive care.
Please let me know if you have any further questions.