A person; male or female that makes you think that you two have common interests and enjoy hanging out with each other only to find out that they talk bad about you behind your back and secretly hate you because they are either jealous or mental.
"WTF?? Mandy was my best friend, I thought. Now she's spreading false and vicious rumors about me to everyone behind my back. I guess, she was always a fake friend and never cared in the first place. She was only out to hurt me from the start."