Sidney's publicist/book agent or whatever she is is pretty much designated as a bitchy "Yeah for innocents getting murdered because now Sidney can do another book deal and my company, and by proxy me, will makes loads more money". So it's really obvious from the start that she's going to be in the body count.
So she's going to her car in the hospital parking garage and the killer calls her, she freaks out and runs to her car, locking herself in. Now, I'm inclined to count this against her, because personally, I would have run straight back to the door she went through to enter the garage and gone back into the hospital where there are loads of people and cops. But technically, she did use an elevator to get to the garage, so she might have been killed waiting for it to get to her floor. (Still, I would imagine there are stairs nearby she could have used). In this case, it's a bit of a fifty/fifty toss up, so I'll say that going for the car is about as good an idea as going back to the elevator.
So she's locked in the car, trying to get it to start when Ghost Face pops up in front of her hood outside with a bundle of wires in his hand. Okay, he's cut the power to her car, obviously she can't drive away. She turns her head for a second as she sees another car driving away and yells for help, and when she turns to look back, Ghost Face is gone. Then SHE GETS OUT OF THE CAR.
What? WHAT? Where is the logic in that? You know he's out there, and you're locked in the safety of your car. Granted, he might have been able to break through the windows and get her, but she was still ten times safer staying in the car than getting out. And most people have things in their car they could use as a weapon; my mom has a hammer/slash knife thing for emergencies in her car (in case you need to break the window and crawl out of the car, and the knife part functions to let you cut yourself out of your seatbelt if it won't unbuckle), that would make a pretty decent weapon. Hell, even one of those chipper/brushes you use to remove snow and ice from your windows would have worked.
Obviously, it would have been better to stay in the car and wait, maybe see if you can get the attention of another car coming by. But the even better thing she could have done is just use her phone and call for help. Ghost Face called her right as she entered the garage, so she's got a working signal. And again, there are cops right in and around the hospital. Someone would have been there to help her in like five minutes.
But of course she doesn't. She gets out of the car, runs for the door and gets caught and killed.
