Starts with The Originals (on now) and then progresses to The Vampire Diaries. It may be the most cringetastic audience, but the moderator is good, and the cast is doing great dealing with the incessant screaming. I swear, the entire fanbase is not screaming girls, but it really doesn't seem that way, based on this particular crowd. I have faith in this moderator. (The moderator for the Parks & Rec panel was awful. Fangirling everywhere.) If you enjoy one or both of the shows, you might enjoy the panels. If you are a squealing, giggling girl, you'll fit right in. If you are irritated by squealing, giggling girls, how good are you at tuning out white noise? I adore Julie Plec, the showrunner and co-creator of both shows. Big fan of hers and her smarter-than-they-should-be shows. You should watch, just for a smart, lady-showrunner.
ETA: no, that's not true—Patton Oswalt was the moderator for Parks & Rec, and it was awesome. I think I was thinking of the Sleepy Hollow panel. I've watched a lot of these, and they're starting to blend together. I do remember that girl, though, and her fangirling and her inability to cheat to the camera and her hair that was styled downstage, so we never saw her face.
ETA: TVD's moderator might have the other girl beaten for worst. Off the rails and no hope of getting back.