It's literally click in the share icon and choose "Share over QR".

The device then will do the "run a server with the file, create the QR Code for access, display it". Your mum has no need to learn how to run it, just how she doesn't need to know anything about how airdrop works to use it.

An app like "Share via HTTP" does that for you.

https://play.google.com/store/apps/details?id=com.MarcosDiez...

It's the same difficulty. They used techy terms because we know that's what's happening, but your mom doesn't need to know those terms or anything like that.