How to get rid of split screen FOREVER?

my senior mother gets very upset when split screen happens. She doesn’t want it. She’s stopped using ’her computer’ (iPad) apart from watching her church service.

stop forcing changes like this on people who update for security patches.

Presumably you have updated your iPad to iPadOS15.x

Unlike iPadOS14 and earlier versions, multi-tasking cannot now be disabled from settings. Multi-tasking has received a significant overhaul, both simplifying its use and introducing new controls.

Key to accessing and controlling multi-tasking split and slide-over views is the small “three-dot” button that is found at the top-centre edge of the screen.

More information about using multi-tasking can be found in this support page:

Use multitasking on your iPad - Apple Support

The iPad User Guide is also a rich source of information about using iPad and its many features. The Guide is available both online using a web browser (such as Safari), or as an Apple Books download:

iPad User Guide - Apple Support

https://books.apple.com/book/id1567104892