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I'm not sure I have had a single MacBook fail, apart from battery, I just keep passing them down... I know my folks have one that's at least 10 years old, anything post 2009 will be solid but I'd go for a 2012 (or newer) MacBook Pro (13inch) as they can run the latest macOS (Catalina) and very reliable and serivcable.
Also a good choice (due to retina screen and SSD)...
https://minkosmacs.com/index.php?route=product/product&path=80&product_id=87
I'd go Apple for sure... grab something refurbed.... all her current devices will sync and share accounts and info, plus Apple laptops (tend to, apart from the recent keyboard designs) last a long time.
My nephew got a cheap second hand 2009 white Macbook and its still running fine (once I replaced the HDD with an SSD).