When I had a-fib, they were constantly checking my ankles for swelling. I would call the cardiologist, especially if this is a new development.
I understand some heart meds make cause edema too. Sorry, I can't remember which meds.
Swelling in the ankles is not normal and is often a sign of fluid overload. Has she ever had CHF? Does she have any other symptoms ie difficulty breathing, coughing, inability to lie flat due to breathlessness?
I would definitely put a call into her cardiologist.
Good luck!