@tony83 I absolutely agree with
@ianf0ster - I was a T2 on insulin for over 4 years and I do believe the insulin resistance got worse over that time.
Because it is likely that I had undiagnosed diabetes for maybe 20 years my pancreas is pretty well wrecked but by going LCHF I have come off insulin completely and am on no other meds.
Because of my dodgy pancreas I do have to limit net carbs to 20g a day. My hba1c was 125 when first diagnosed, was around 52 on insulin and on LCHF/keto it is 36. So for me it has really worked.
I did wonder if - because this rise is so sudden - whether your wife has a virus or infection which would play havoc with her blood sugars.