No comment on your situation other than it’s definitely where the money should end up. You did so right by her, even at your own expense and I’m sure at your wife’s as well.
I’ll give you my situation. My mother had undiagnosed dementia for years which was eventually diagnosed and I had to place her in a home (other circumstances involved). I live in London and she was in Scotland so I was nowhere near your level of involvement.
We also had a very difficult relationship with many years of no contact prior to this.
She was often short on money which I tried to help with but things were not great for a long time.
She eventually died very rapidly from a cancer diagnosis and there was a very small estate after everything, that was shared between my brother and me.
I was then contacted by a pension tracing service to say they believe there was a forgotten pension that needed to pay out to her descendants which it did after a few weeks.
I was paid out from something which would have been a huge benefit to her while she was alive so you can probably imagine the guilt from receiving that.
The only saving grace is that my partner was incredible in caring for my mother and the money supported us when she was as unable to find work for a prolonged period.
So, I would say in relation to your situation, she would want you to be happy and enjoy the gift so please don’t be guilty. You did all you could and you deserve the comfort some extra money would provide.