Molly,

I would agree that your sister should see the doctor for her ear ache...but the good news is that I also got aches in my ear after surgery and radiation. About a month or so after radiation ended. When I ask my ENT he said it was a good thing. It was the muscles and nerves coming back.
They have faded now and happen very infrequently. It's sharp pains that only last a few minutes.
As I said - he only said this AFTER looking and confirming nothing else was going on.

Take care,
Dinah