I installed Ubuntu for many people in their 80s. Give her some time with FF, you don’t have to remove chrome, just hand her FF. I bet she does just fine.
If you do, you acknowledge that "Chrome disabling uBlock Origin is a serious security threat."
If you don't, then "Chrome disabling uBlock Origin is a serious security threat" seems even more true.
Either way, I'm curious on the size of your bet here. Talk is cheap, and you've only given OP the laziest and most obvious solution. Do you believe what you said is profound and/or an interesting argument?
I’ve had both experiences myself. Sometimes the older folks manage just fine. Sometimes they don’t. Sometimes it’s an aversion to change, sometimes it’s to cope with cognitive decline, and sometimes they just like one thing or the other, just like anyone.