Can you just get an open box laptop? Some computer recycling places in big cities will sell them for like $100-$200, perfectly adequate for what you need. Best Buy also has a bunch of certified open-box (but cleaned up, tested, etc.) laptops that are great values for generic usage like this.
Stay away from tablets; they’ll just be endless headaches for whoever ends up having to support your friend as she learns and relearns everything.
I think her scenario screams out “chromebook”. If you are able to be on hand to set her up with it she’ll be up and running in no time. It’ll already have a decent keyboard. Ports are available for LAN and mouse and there’ll be no buggering about with Windows updates and very little friction to learning the browser and email in the chrome OS (certainly no more than a tablet). $200-$300 would get a brand-spanking new one with a 14/15 inch screen.
For her usage they are perfect, rock solid and pretty foolproof. I set my MIL up on one remotely and she had very similar simple demands and she loves it.