Take a full day and tell her to do the "hop on hop off" bus tours. There are 3 lines, blue,red,green... She'll see ALL the historical buildings with Gaudi, Tipidabo, the FC Barcelona futbol stadium, the 92' Olympiad grounds, the port and many many other places that make Barcelona beautiful! Check out Las Ramblas, A Flamenco show and of course the beaches! You'll hear the call of alcohol all day being yelled out by vendors scouring the beach! "I have mojito, sangria, cerveza, agua... " Its fun! The last 2 days, get on the train, head 40 minutes south to Sitges, Spain and really start your vacation there! Beautiful beautiful town, small, friendly, a lot of energy, great food, perfect beaches! "El Rancon de Pepe" is a restaurant there! Great food, good Sangria! 3 days probably isn't enough time to really get into all the fun cultural experiences Barcelona has to offer but its a start! Enjoy! Ciao!