Visible crew/equipment: At the end when Sidney's dad falls out of the closet, if you look closely you can see the hands of a crewmember who was in there too, pushing items out after him. (01:42:40)
Visible crew/equipment: When Casey tells the killer "Dial somebody else, okay?", you can see the shadow of some equipment on the decorative pillar at the top right of the screen as the camera moves backward. (00:03:18)
Visible crew/equipment: When Casey agrees to play the killer's game she crouches down next to the television and as the killer says "Here's how we play..." you can see a clear shadow of the head of the boom microphone cast on the white wooden railing at the top right of the screen. (00:06:25)
Visible crew/equipment: Look closely (you may need widescreen to see it) at the railing when Sidney is walking up the stairs outside in her parent's wooden patio talking to Tatum on the phone. You'll notice a quick boom shadow on the right of the camera as it's backing up. [Noticed also by Wes Craven on the DVD commentary track]. (00:22:25)
Visible crew/equipment: There is camera equipment reflected in the door window when leaving the police station. (00:36:10)
Visible crew/equipment: When the officers take Billy away from Sidney's house, a set of lights is reflected in the back window of the car. (00:31:00)
Visible crew/equipment: When Drew Barrymore runs away after the killer just called her 'blondie', there's nobody behind her character, and yet a new shadow is cast on the wall to the left when the camera follows her around the corner to lock the front door. (00:03:50)
Answer: Characters in horror movies are notorious for not doing the most obvious things. It's most likely that she was scared and not thinking straight at receiving numerous threatening phone calls, particularly when she is threatened after hanging up on the killer.
Manky
Also, when she told the caller that she was "two seconds away from calling the police", his response was that they'd never make it in time. She also knew he was nearby as he made comments that indicated he could see her. She didn't know it was someone that knew her. She's a teenager and scared, so her judgement was clouded. She reached a point where she believed her only chance was to get away from him by either fighting him or getting out and hiding somewhere outside.
dewinela