Can someone who watches True Blood clear this up for me?

I'm only on season 1 so please don't give anything away. I'm watching the episode that Sookie's g-ma gets slaughtered. The poe-leece are commenting on how Bill was already at the house when Sookie found her. That's cause she drank his blood, right? But then I got to thinking, this drug called "V" is just vampire blood, right? So how come it's making her brother trip out and none of that happened to her?