Apart from the Meteorite story I believe this is the most plausible theory. It's one of the Knapps. Maybe one who hasn't lived in Mayfield place so that Rumsfield didn't recognize her. A sister or maybe even granddaughter from the Knapps living in Mayfield Place.
The Klopeks didn't care and just left the picture where it was.
The Knapps were old people atatched to there house, so if the girl in the frame was a Knapp relative, I would guess grandaughter. And if this is correct, then to the Klopeks, the picture really would have "came with the frame".