Older relative knows but cannot type her iCloud password correctly

My 85 year old great aunt, who lives on the other side of the country, cannot type her iCloud password correctly after her iPhone was auto updated to iOS 15. I checked her password on iCloud.com, so that’s not the problem. I repeated it character by character, confirming that she had capitalization correct, and ended up with the correct number of dots after finishing.

No luck. After this failed four times, I told her to take it and the carefully-checked password to the trustworthy local branch of her mobile service provider to type in for her on Monday, because she needs to have a cellphone before we’d next see her!

Any tips for older relatives who cannot quite type things exactly any more, and live too far away for us to intervene on short notice? She only needs to enter that password after major updates, and only cares about using our country’s vaccine certificate app.

Aside from her password and the answers to the three password reset questions, anything else she should bring to the shop? Yes, I know that she’s putting an awful lot of trust in a mobile phone shop employee, but her iCloud account is extremely uninteresting.

Unfortunately there are no remote control solutions for iOS (just remote viewing).

I would try a wireless Bluetooth keyboard or get Apple's Lightning to USB 3 Camera Adapter and use a wired USB keyboard.

Ideally the keyboard would be connected and configured before the update.