Michelle Trachtenberg and Sarah Michelle Gellar
Rick Diamond/Getty; Fernando Allende/Splash News Online
05/15/2009 at 04:00 PM EDT
How did Michelle Trachtenberg feel when she heard pal Sarah Michelle Gellar was expecting
? "I was jumping for joy," said the actress, who played Gellar's little sister on the show Buffy the Vampire Slayer.
"We talk every other day. I'm super excited!" she added at a private dinner for designer Rebecca Minkoff and stylist Ilaria Urbnati's at L.A. boutique Confederacy
last week. "I'm so very happy for her and Freddie. She's going to be an extraordinary mom. Good people make great parents."
This will be the first child for Gellar, 31, and Freddie Prinze Jr., 33, who have been married for six years. Trachtenberg says she can see the key to their longevity: "It's in the Ben Affleck
, Jennifer Garner
or Gwyneth Paltrow
, Chris Martin vein – they really don't talk about their relationship. They keep their private, personal love life to themselves. That's what makes it so special."
Trachtenberg takes her own close-lipped advice when talking about her recurring role as Georgina on Gossip Girl
, but assures that next week's episode, airing Monday on the CW, will "definitely have a sweet, fantastic cliffhanger" that will reveal if Georgina's resurfacing evil is here to stay. Trachtenberg will also star in NBC's upcoming nurse drama Mercy