Create a normal user account for her instead of an admin account; though that means that you will have to install programs for her whenever she wants anything installed.
Also, buy her a decent security suite. I'm partial to Eset. Kaspersky is good too. Don't bother with Symantec or MacAfee.
Last, I recommend installing an ad blocker on her browser. The number of phone calls I got from my mother fell significantly after I installed an ad blocker on her browser. No more "this popup is telling me I have a virus" or "which download link do I click" phone calls. I recommend uBlock origin as it gets around most anti-adblock stuff. Still, some sites don't work well with ad blockers, especially streaming video sites (Hulu comes to mind), so...