That was a pretty poor reason. (SPOILERS)
So... I'm gonna be blunt: I hated Laura a lot worse than the people she was antagonizing.
Spoilers incoming. Alrighty. So, Laura gets passed out drunk and sharts herself. Alright. Bad feelings all around, a few people go full troll on her, then she guns herself down in public. Um. Alright. That's a pretty goddamn weak reason, but whatever. One year later, comes back to kill all her old friends and stand on the "oh, you all have secrets too!".
Laura, my dear, welcome to Humanity 10-frelling-1. People have secrets. It's common human nature to have this. What isn't common is to want to, and successfully, kill people over it. Embarrassing? Sure. But you're supposed to suck that up, buttercup, and get on with life. Not end yourself then come back for them. After she did die, all they did was say kind things. They felt like crap.
But you? You made the choice to end yourself. You went full on drama queen because you made a stupid, and then came back and murdered a bunch of relatively innocent people (standards of innocence may vary from beholder to beholder).
I'm sorry. I couldn't feel bad for Laura. At all. Worse, I actually came off wanting Laura to get purged and sent to the fiery hooks of Hell. Or whatever other torturous afterlife you can think up. She was a terrible person who literally killed people over a stupid frelling video. Sadly, that was not an option: Once again, as is most ghost movies, there is no way to protect or dispel the ghost, and we already knew the ghost knew who put the video up, so why kill everyone else?
I realize I'm overthinking a Ghost Movie, but when people are going on about how it "raises the bar of horror"... and I'm getting bored like, halfway through the movie, I feel I need to step up and say something. People say the best aspect is the story, when the story pretty much seals the deal that Laura was a whiny little drama queen who talked crap about everyone else, then when they kicked her down a peg, ended herself and then came back to kill them all. Over a video of her sharting herself.
Unless of course the entire movie was trying to say "Pretty much everyone's an *beep* even the supposed victim in all this". Then I'd just say "Um... sorry, but your attempt at being Forget Me Not failed. Badly". The least they could have done was make Laura more of a sympathetic character. Finding out how she was alive and after death pretty much sealed the deal that she was a terrible person that the Earth was better off without.