I am so sorry that your Abbey has EPI, it's a horrible illness
Nikki uses two 12 oz bottles of Viokase per month so I feel your pain but her insurance takes care of hers.
I would suggest getting your enzymes from Diane, that should save you a lot: Enzyme Diane -
I would also keep daily notes on what you are feeding, how much enzymes, poop quality, etc to see what's working and what's not. We have been doing this for over two years now and it helps a lot.
I would like for you to join and read through this group, a ton of great info, it helped me so much when Nikki was first diagnosed: Forum - EPI * Exocrine Pancreatic Insufficiency
Also, if your vet didn't do this already, I would get her cobalamine/folate checked because most EPI dogs have SIBO and often they need B12.
Serum Cobalamin (Vitamin B12) and Folate - Texas A&M Veterinary Medicine & Biomedical Sciences