Reading Journal

My main question is how could Cassidy forget so easily about her boyfriend, even when she's in his arms?

"Cassidy couldn't believe that she was how jealous she was getting over someone who wasn't even her boyfriend."

Casssidy is falling for a TA at a French summer program she is attending, and after only knowing him for a short time, and it seems as though she prefers him over her boyfriend of two years. She was becoming really jealous of the TA when he was talking with her friend, and it's very strange how she is doing this, and it is implied that she doesn't even know why.