It might sound like a pretty obvious thing, but have you tried changing the tools into the "Tabbed ribbon" that office uses instead of the classic old 90s organization scheme in options ?
I have come to notice that when people who don't really work with computers very well, in particular boomers, say that they can't stand LibreOffice, they mean they don't like the layout of the tools, because they can't find anything they need. I suppose they just got used to where everything is with modern office.
Just change it and see if she will like it better. Usually solves it for the boomers i help. Nothing is holding LibreOffice back more than their default layout scheme. They really don't know their target audience's pain points AT ALL. Just goes to show why you need to study your users using the product without being explained anything.
I don't get why their default is a layout that has been outdated for 24 years. Nostalgia or what? Only really old people who used computers in the 90s a lot will intuitively find it useful.