Why my daughter (2 years) always say no to sleep although she is very very sleepy?

Testing limits is : her job at 2; your job is to set limits for important things like a consistent bedtime. An hour before that time, let her choose her pj's, give her a warm bath, brush her teeth. Let her choose the story you read her. Put her in bed when she's drowsy, but awake. If you completely & consistently ignore her protests as they get longer & louder in an attempt to get your attention, they will stop.