Ridiculous endeavour (attempt No. 23)
George Longstaff custom made 1992 frame for my 'late' (never understood that bizarre term) wife. Years spent on and off trying to make it fit me.
For me there came a time when I accepted that a bike I had always loved didn't - and would never - fit. But it took a custom made bike to realise this. Nevertheless I held on to (and still rode) the old one out of sentiment.
Then one day I found someone (who had become a friend) that it did fit, and I gave it to him. That was hard, but also liberating.
By 'late' do you mean dead? If so, I can understand wanting to keep the bike. I hope it does fit your step granddaughter down the line, and that she loves it.