A frozen angel is the girl that is incapable of keeping alive a long, lost but valuable friendship because of a crush from a guy she does not want. Frozen is referred to the behavior of unreactivity to all efforts of keeping friendly contact (regardless of methods such as GSM, internet, through mutual friends or even face to face). The word angel that completes this phrase refers to the specific girl who's existance in a guys life made the difference for the better.
Person 1: Man, forget that bitch who rejected you, move on, there are plety of fish in the see.
Person 2. She is not a bitch, she used to be my good friend but after I aked her out, she turned into a Frozen Angel.
Person 1: So on the other words, she does not want to leed you on, or be there to witness efforts of trying to make her jelous?
Person 2: Exactly.