My 4'11" wife has the same problem (in many vehicles).
I got some of those anti fatigue mats from Harbor freight, and cut them to fit so they can't slide around, basically making the floor come to her. (it took two layers screwed together to make it comfortable for her).
https://www.harborfreight.com/catalo...ti+fatigue+mat
Doing that solves the problem for her. Now she can have a heel on the floor and toes on the pedal, rather than just toes on the pedal - which as you know is a very awkward driving position.