Any of the large, easy to use distributions should work just fine. I’d recommend a popular distribution because it’ll be easier to get help online. So consider Mint, Fedora, OpenSuse, Ubuntu and maybe Pop!_OS.
I think the main consideration should be which DE (desktop environment) she’d like to use. IMO the main contenders would be:
Based on which DE she prefers, I’d suggest getting a distribution that comes with said DE by default, for the best possible integration. How do you figure out which DE she likes best? Put Ventoy on a USB stick along with a few different Linux ISOs. Ventoy wil let you choose which one to boot from a menu. You could get the following ISOs:
Download an ISO for each, install Ventoy on a USB stick and copy the ISOs to the stick. Boot into each ISO and play around with the desktop for a bit. When she’s figured out which DE she prefers, install a distribution that comes with that desktop.
I installed Windows 11 Pro 24H2 yesterday and the oobe\bypassnro trick worked for me. You just have to make sure no ethernet cable is connected. Then if you tell the installer you have no internet, it’ll let you create a local account.
I’ve been using Linux for about 25 years. I completely stopped using Windows at home more than a decade ago.
I do some volunteer work for an organisation that refurbishes old computers and gives them to people who can’t afford one. For the time being we’re using Rufus to bypass TPM and other hardware requirements so we can install Windows 11 on everything.
We’re willing to install Linux for people who want it, but unfortunately I haven’t seen that happen yet. Most of our customers have no idea what an OS is. A lot of people also need Windows for education or work. There’s a free course available that teaches how to use a computer and of course that is also Windows-only.
We helped one of our colleagues to install Mint on his old laptop, though.