"That bitch! She tricked me!" Amber Tamblyn told PEOPLE about how she found out that her Sisterhood of the Traveling Pants costar had given birth.
Tamblyn, who was out to support her other Sisterhood costar and good friend America Ferrera at the launch of Ferrera's husband Ryan Piers Williams's art exhibit "Monsters and Landscapes" in N.Y.C. on Friday night, was clearly kidding about the bitch part – but she definitely got duped.
"I went up there and I didn't know, everybody knew but me, and she does that s--- to me," Tamblyn jokes of Lively. "She was texting me about wallpaper, she was like, 'You gotta come see my new wallpaper,' and I went up there, and there was her baby."
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She added, "I took pictures with Ryan and the baby and sent them to Ken Kwapis, the Sisterhood director."
Ferrera is just as thrilled about Lively's little one. "I couldn't be more excited for her and Ryan, and they are going to be amazing parents," she said.
"Monsters and Landscapes" is open to the public through Jan. 18 from 10 a.m. to 6 p.m. daily.