Have her practice putting together jigsaw puzzle from this site.
https://www.jigsawexplorer.com/

It'll help her get use to using her mouse and tell her after clicking onto the picture of the puzzle she wants to play, she'll be given some options, show her how to mouse over the options to see the name of the options she has. Have her first click onto the "pieces" option and choose a smaller number of pieces than what they have chosen for the puzzle, also have her change background colors till she finds one where she can easily see the pieces on.

After that, walk away and tell her to howler if she needs any help.

She already knows from being a teacher, that the more you repeat a process, the more likely that you will retain how to do it which is why the jigsaw puzzles works for that. It teaches her how to left click onto a picture, mouse over to see the names of things/options and it helps her with coordinating her eye hand movement and dragging ability.

Also when she chooses the option of "Play this puzzle", it will open in a new tab, show her how to close that tab and also show her where the back arrow is so after closing the tab, she can go back to the puzzle home page.