Why do girls do this?

My nephew turned 8 on April 21 and we went to the Marlins game. The whole family went out there, 11 people. The Marlins were playing the Mets and The Stadium formerly known as Pro Player which was formerly known as Joe Robbie turned into Shea Stadium. The place was infested with Mets fans. After the first inning, I ran to grab a beer for myself and my aunt. When I returned, the seat next to me was filled with what I thought was a cute girl. She had green eyes and long lashes, in a wife beater and jeans. I am thinking sweet... So eventually we sparked up a conversation and I learn she is a Mets fan. However, she still seemed cool so I did not hold it against her. Her name is Danielle and she is a St. Thomas Law Student.

Now, lets fast forward to the 8th inning. I ask her if I could call her next week so we can hang out. She paused and was like uh, sure... Right then I am thinking she doesn't want to but she did. I still have a chance to hook up even though the present does not look promising. Marlins hit, the Mets hit, and the Marlins hit again.... Game Over. I turn to her and she has already scurried away, up the steps and making sure to avoid any and all eye contact! Not only did the present go dim, the future doesn't look so great either.

Why do girls do this? She knew I was there with my entire family. She could have atleast tossed me a bone so I wouldn't look like such an ass in front of everyone. Does she think she is being nice by giving me her number and then shunning me later? Why don't girls learn to just say, "I am flattered, but I would rather not." No games, no lies... just basically tell us thanks but no thanks.