First off, I am
so sorry for your loss. And, yeah... Grief'll throw a wrench in, and if it was due to diabetic complications, I can see there'd also be a part worry in there as well. Not likely to kick up your HbA1c that much though, but it certainly won't have helped.
You mention the measures you've taken, but I'm missing a rather massive one. What's your diet like, what are you eating? Diet drinks CAN spike blood sugars, so that might be a problem after all. Some are fine drinking them, some aren't. You may be in the aren't category.
As for diet, and sorry if I'm beating a dead horse, almost all carbs turn to glucose once ingested. So that's not just sugars, but starches too. Bread, rice, pasta, cereal, corn, potatoes... They can be more than a little problematic. If you cut those out, stick with meat, fish, poultry, eggs, cheeses and the like, above ground veggies, leafy greens, olives, that sort of thing, you'd likely fare a lot better.
https://josekalsbeek.blogspot.com/2019/11/the-nutritional-thingy.html might help a little. Though, I don't know what meds you're on, you would maybe have to be very careful of hypo's, so do test plenty.
You can do this. You will do this. Your signature is right. Just have to find the right method for you.
Hugs,
Jo