Awwwww. I think that look is "ok, so where are my new treats?!?" :lol:
Sounds like you are getting things on track. Did your vet mention Cosequin for the arthritis? If not, I would ask about that. It's a supplement you can sprinkle on their food - I don't know how it might affect BGs, but from what I understand it can really help with arthritis. Some also use pain meds for it - I'm not sure which ones, but you could post on Health for arthritis suggestions and I'm sure you'll get some good ideas. If she is at the point of hissing then she is surely in some pain. I'm surprised your vet said there is nothing they can do, I think there are quite a number of things. Some may have undesirable side effects so I would be careful in deciding what to do, but still I am pretty sure there are options.
Did your vet start you out at the doses at the beginning of your spreadsheet? Or did you start at a lower dose and move up gradually? In either case I agree you do need to stick with a lower dose for a few days and get some data to be clear if a dose increase is warranted, and then move up in doses if needed, knowing for sure that you are moving in the right direction.
Also I think if you switch up to LC treats, you may see a difference. Hard to know for sure, but even a couple bites of something higher carb can really make their BGs skyrocket.
Finally, are you checking for ketones? Does she have any ketone or DKA history?