"Of course you do. What was he like?"
Of course, having asked that would not actually mean that I cared what the answer was, and would certainly lead to a long monologue on the wonderful traits of someone I have no interest in hearing about, but it's the polite thing to do, so I would listen, nod and occasionally say "Mm-hmm," and "Kewl," and try to remember a few of the pertinent points in case they came up in conversation again at some later date.
It's dull and tedious, but just the sort of thing one does for those you like.
Her ushering you out the door, on the other hand, does not necessarily mean she was offended by your silence. She may simply have had other things that needed doing. Ask about her Dad some other time, "So tell me about your Dad, what did he do?" she'll be impressed that you were interested enough in her to inquire and that you remembered to do so.