Aunt Opal? Does that sound right?
ETA: Found it. It's actually in BGDF:
Martha: Dad's fine. But your Aunt Opal broke her hip, so I flew in to help out.
Clark: A broken hip on top of a ruptured gall bladder? She fall out of her hospital bed?
The fact that Martha flew into Metropolis to help out, would suggest, of course, that Aunt Opal lives there.
LabRat