Dont stress too much about giving her sister a hug. I made the same mistake when I was leaving at the Airport, I gave Rhoda's sister a handshake then said out loud "hey give me a hug" knowing what I was doing was not accepted but I really dint care because I was leaving. Her sister was uncomfortable but it was at the airport and she did hug me goodbye back. It happend, no harm done, but I wont do it again just because it made her feel that way.