"I was a vegetarian for many, many, many years and all of a sudden I started to crave red meat," Thiessen tells PEOPLE at Thursday's USA network and Vanity Fair bash in New York. "Crazy enough, I had a steak before I left tonight and I would never have eaten one before. One day I just woke up and craved meat."
In addition to steaks, the White Collar star, 36, is also enjoying foot rubs from her husband, Brady Smith.
"He rubs my feet, my shoulders and he always gets anything for me even if I'm all hormonal," she says. "I have the best husband and he's a sweetheart."
As for whether the two will be decorating the nursery pink or blue, that's top secret – at least publicly. "I couldn't wait to find out," Thiessen, who is keeping the baby's sex private, says. "Are you kidding? My husband I were way too excited to wait. We needed to know right away."
Though she will be a first-time mom, the actress's White Collar costar Matt Bomer says Thiessen's maternal instincts are already in full gear on set. "She's totally the den mother of the show," says Bomer. "She keeps us guys all in check and she makes sure that we are gentlemen. She's so organized and so loving and generous – that can only make her an absolutely amazing mom."
Meanwhile, Thiessen's White Collar husband Tim DeKay, a father of two, has already given the expectant mom some parenting wisdom of his own. "I told her that being a parent is like the Peace Corps. It's the toughest job that you will ever love," says Dekay.
As for experiencing her changing body, Thiessen is taking advantages of her new curves. "The best part is not having to suck in your stomach anymore when wearing a tight dress. I love it!"