Best way for a newbie to learn how to use the iPad

Perhaps begin with reviewing the Tips App - already installed on every new iPad.

The iPad User Guide is a rich source of information and guidance. 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

The Guide begins with basic information - and then has a detailed section for each of the Apps and/or specific features of iPad and iPadOS. The downloadable version is a more-readable “book” version of the Guide - while the online version is perhaps more useful for quick “lookup” of something specific.

To LotusPilot's excellent suggestion, I'll add the advice I used to give to people in my classes when I was teaching people how to use smartphones and tablets. Don't be afraid of making a mistake. That's the best way to learn. Play with it. Tap on everything and see what happens. All those little kids who seem to have been born knowing this stuff? That's how they do it.

Also, tell her to make an account here so she can ask questions and encourage her to ask lots of them!

A point very well made - and thoroughly endorsed 🙂