Edema associated with itching can be due to hypersensitivity reaction . There can be other reasons also
But needs to be evaluated.
As i have no idea about the medical history of your mother so wont be able to advise much.
Send photos if possible.
Next Steps
keep her leg and hand elevated while lying down can be done by keeping pillow under the leg and hands.
try to notice the trigger factors.
reduce salt intake.
can use antihistamine drugs for itching
Health Tips
consult if possible for you.