The reason the gal character finds the flowers gross is foreshadowing.
She can see and speak to ghosts. That's why she dropped the phone. It wasn't an accident. But she can't go up against the psycho bitch. I think that's also why she was pulling her phone out, she was trying to take pictures of the ghosts.
And yes, crazy bitch is even worse than what we've seen so far. WAY worse.
As far as I can tell, the manga basically revolves around the ghost duo either dealing with their friends psychological hangups that were just barely held together before all this shit started happening, alongside trying to keep Chiaki from killing everyone else.