because she's falling for him :p but she tries to protect herself, she's way too scared ^^ plus he's supposed to be gay
Remember when she was really friendly with him and was having a nice time, since shes falling for him, this probably never happened to her before. Shes so used to being by herself and being independent all her life. Shes lashing out at him because this is a first and shes probably really scared.
Cuz she's falling for him and is jealous that she'll never have a chance (in her mind anyway cuz she still thinks he's gay).
How could she be so cold towards him （/TДT)/