Credit: Kevin Mazur/

A pregnancy glow certainly suits Jessica Simpson -- just ask her sister, Ashlee!

Attending Sunday's Screen Actors Guild Awards on the arm of her Boardwalk Empire beau Vincent Piazza, Ashlee, 27, told E!'s Giuliana Rancic first time pregnancy sure agrees with Jessica, 31.

"She's amazing," Ashlee said of her older sister, who's expecting her first child with fiance Eric Johnson later this year.

Despite craving high-sugar foods like buttered Pop Tarts, Kraft Mac n' Cheese and Cap'n Crunch cereal, Jessica appears to be keeping her figure in check.

"She's looking good and feeling good," confirmed Ashlee, who turned heads in her own right in a black beaded Jenny Packham gown and Loree Rodkin jewels.

As she and Johnson prepare to welcome their new addition, the Fashion Star mentor's positive energy has rubbed off on those around her.

"She's completely content, so happy," Ashlee (mom to Bronx, 3, with ex Pete Wentz) told E!'s Rancic. "It's fun to be around her. It's like 'yeah, I want some of that.'"

Announcing her pregnancy on Halloween by posting a mummy-themed Twitter pic, Jessica and Johnson -- who put wedding plans on hold until their baby arrives -- couldn't be more thrilled to become parents. "We can't wait to meet our baby!" Jessica told Us Weekly.