So I'm the full time caretaker for both of my grandparents. My grandma is a diabetic and has been in an insulin pump for 20+ years. In the past year, she's gone through 4 total pumps because she swears they aren't working because her sugars are so high consistently. I managed to keep her pretty stable around where it needed to be over the past 2-3 months by doubling the amount of insulin she would get per bolus. Her last endocrinologist visit had the doc be like OH YOU'RE SO AWESOME THIS IS GREAT MANAGEMENT HER A1C IS DOWN THIS IS GREAT and proceeded to fuck with the settings anyway, and since then (about 3 weeks now), her sugar has been completely out of control, going back to the settings I was using hasn't helped, and a brand new pump came and the same thing is happening.
I'm really at a loss. There's no way 4 pumps in a year have malfunctioned exactly the same way, and she won't believe me that diabetes gets harder to manage the older you get, and being constantly stressed out and depressed is going to give wild readings no matter how stringent we are. I weigh and track all of her meals so I know exactly how many carbs she has and what size bolus she needs and it just....isn't really working anymore. She keeps getting on me that I need to get them under control, but I'm doing everything I can and she just won't accept that it's not the pump.

In my experience old timers try to cling onto something so they don't lose hope. It's usually a type of medicine, a doctor they like or a medical device that has helped them.
Even though their health might get worse... if they keep taking this pill, this machine keeps working or this doctor checks them up everything will be alright.
To acccept that the machine isn't failing is also to accept that her health is deteriorating. Which is a reality she probably doesn't want to come to terms with.
As sad as it is, if you pretend to mess around with the settings to improve it, you might actually cause some sort of placebo effect that makes her feel better.
At the same time in as strange way that might relieve some of the stress and actually improve the readings somewhat.
My grandmother lived through WW2 as a young mother and was malnourished so after the war when life returned to normal doctors prescribed vitamin supplements.
She always had an obsession with those vitamins, force feeding them to her kids basically because that was the thing that was going to 'save' them of any disease.
As she got older she kept using more and more vitamins, because those were the things supposed to make her better.
Of course, no vitamin could treat the illnesses she had at that point but in a weird way she felt better after taking them even though there was no reason for it. Always trying new types and brands.
During a heated exchange with my dad and uncle, who had arranged for her to be admitted to a care center when I was about 8, she threatened that she would kill herself by taking a large ammount of pills.
She grabbed the bottle and I ran out the door crying. Years later I put things together and realized it was the same vitamins she was obsessed with mixed with aspirin and tylenol that she had kept in that bottle.
It couldn't have possibly killed her even if she ate the whole bottle but my 8 year old self was traumatized by that experience.
She clung on for another 6 - 8 years or so to become 92.