I finally talked my mom into replacing her 2008 MacBook (El Capitan 10.11.6) with a 2019 iMac (Mojave 10.14.5). Last year I bought her a WD Passport Ultra 1Tb to serve as her Time Machine. I have a 2016 MacBook Pro (High Sierra 10.13.6). I backed her 2008 MacBook up tonight with her Passport...