You can adjust the thermostat via Nest app. I use it when I'm too lazy to get out of bed to adjust the settings.😁 I haven't tried the app on a tablet yet, but I imagine the UI scales up so everything should look bigger.
I use the Nest with it's app, very handy set temps when in bed! I don't know how tech savy your mother is but I would look into a thermostat that is programmable with different temps during the day/night. Once it is set up for her, she should be comfortable. The nest loses it't network connect every now and then and it constantly wants me to use Google log in. I got the Nest before Google bought them, and don't anything to do with Google in my home network.