Amber Tamblyn reveals her daughter's name, sharing special letter

— -- Weeks after Amber Tamblyn and David Cross welcomed their first child together, the new mom has revealed their daughter's name -- with the help of a very important friend.

The "Sisterhood of the Traveling Pants" star took to Instagram Monday to share a letter from Hillary Clinton addressed to baby Marlow Alice Cross.

"Dear Marlow," the letter read, "Happy Birthday! Your birth has been a source of great joy for your parents, Amber and David, and your vast community of admirers and champions. I send my best wishes to you for a lifetime of amazing accomplishments and adventures, full of love, learning, and friendship. With warm regards, I am -- Sincerely yours, Hillary Rodham Clinton."

The letter was dated Feb. 15 and signed "Hillary."

Alongside Clinton's message, Tamblyn wrote, "The one day I decide to put mascara on Hillary Clinton sends us this letter for our daughter. Crying now."

She continued, "A letter from one spectacular woman who has lived so much to another who has only just begun. My heart is as full as this diaper I'm about to change. Thank you, Hillary, grandmother to us all."

Last month, Tamblyn, 33, and Cross, 52, announced the arrival of their first child by posting a video of a tiny foot wiggling out of a pink blanket. But they joked about their daughter's name.

"David and I are proud to announce the birth of our daughter," Tamblyn wrote on Instagram, "Dauphinoise Petunia Brittany Scheherazade Von Funkinstein Mustard Witch RBG Cross Tamblyn-Bey jr."

The couple were married in 2012.