Thank you for asking your question.
Your description of your mother's foot points towards a reduction in blood supply to the foot, Peripheral Vascular Disease
In this condition, blocks develop in the arteries of the legs that hinder blood supply.
This can be confirmed by feeling for her foot pulses.
Seeing an Interventional Radiologist
like myself would be the right way forward as we can diagnose this as well as open up blocked arteries and thus curing her.
Vascular Interventional Radiologist