a real bitch
A real bitch doesn't lie to your face. She'll tell you straight up, even if it's brutal.
You asked her what she thought of your new haircut. She said, 'You look like a flamingo in a snowstorm.'
You told her your friend was a jerk. She said, 'That's not a jerk, that's a total idiot.'
You tried to flirt with her. She said, 'You're cute, but I'm not falling for your nonsense.'