OP, its likely your mom drives by "pulsing" the accelerator pedal. many people do this and dont realize they do it. My wife drives the same way. "Puush... fully release..... puushh... fully release". If you listen to them drive an ICE vehicle you will hear the engine Rev..... stop.... Rev.... Stop......Rev.... stop" constantly.
I never drove that way to begin with, so it was easy for me to transition to the model 3. My wife cant get used to my model 3 because she drives this way (she doesnt drive it often).
I set regen to low and creep mode to on, for her under her profile. If she drove the car all the time, she would unlearn her "pulse" driving technique, but because she doesnt (and as
@cucubits says its not that big of a deal, energy saving wise, for us), Its much easier for her to just feel comfortable driving it than me trying to "convert" her.
There is no need for OP to "convert" his mom to this. She will either come around to wanting to do it, or not, but it has to be on her own terms not because someone else is pushing it on her.