After several email exchanges I had one who cancelled telling me her mother suprised her and just suddenly arrived at the airport.  

Yeah, right.   Who's mother is going to hop on a plane and suddenly show up at an airport without advance notice?  My mom would have sent me her itinerary weeks in advance to make sure my schedule was clear and that she would not be waiting at the curb for a ride.  You have to come up with somethig better than that.