Hermione hadn't been herself, and she knew it. She knew that the Horcrux was the problem, and that it was affecting her and Harry and Ron and even the rest of their bloody dorm and making them tense and angry and too prone to yelling or, in her case, apparently telling people that they deserved to be murdered. She knew. And she couldn't do a sodding thing about it.
But the fact that she'd heard the rumour going about the Tower that Ginny had been hurt cut through a little of that, and she was at least concerned enough for her almost-a-sister to try to figure out what it was that had happened. She couldn't find Ginny to ask her, though, and to be honest she didn't trust herself with talking to Ginny if she was in a state right now. She'd be too likely to snap at her, or yell, and if something really had happened that wouldn't be good. She knew that she was close with the Capper girl in her dorm, though, so she looked for her instead.
And didn't find her in the Tower, which was annoying and pulled at Hermione's already fraying temper.
She sought Harry out, though, and got a look at the Marauder's Map. The dot that signified 'S. Capper' was currently moving slowly about in the fifth floor corridor, so Hermione gave the map back to Harry (alright, she might have called him a name under her breath as she did, too) and then headed that direction.