Thanks for the query,
Edema of leg might be due to COPD.
Considering the age, the itchy rash on leg can be senile xerosis.
It is a common condition.
A photograph would also help me in giving a closer diagnosis.
Apply a mild steroid
lotion like desonide
In day she can apply liquid paraffin
Also give her an antihistamine tablet for few days.
This will give her some relief.
Please meet a dermatologist
for exact diagnosis.
Let me know if you have any other doubt.
you can ask a direct question to me on this forum, following the below link.
Wishing you a good health.