I guess it depends on how the situation was broached, but I would be extremely unhappy to have to sit in a window seat for a flight as long as ORD-LAX. I actually don't book flights if I can't get an aisle seat. In this case, it sounds like the dad wanted to sit across the aisle from his daughter, not next to her. The mom was already sitting next to the daughter. I'm not saying I would stand firm, but I would not go to a window seat quietly and actually might ask the agent to just book me on another flight or carrier if there was a medical need for the dad to sit across from the daughter.