"I didn't think it was going to happen, but he gets jealous," she tells PEOPLE of her son

By peoplestaff225
June 15, 2016 03:47 PM

Molly Sims is trying to keep the peace in her home.

“We have a little sibling rivalry going on,” the 43-year-old told PEOPLE at the Max Mara celebrates Natalie Dormer as the 2016 Women In Film Max Mara Face of the Future Award recipient event in West Hollywood on Tuesday.

Sims and her husband, film producer Scott Stuber, welcomed 14-month-old daughter Scarlett May last March. The couple’s baby girl joined big brother Brooks Alan, 3.

Jon Kopaloff/FilmMagic

“I didn’t think it was going to happen, but he gets jealous,” she admits. “He wants to be held. He wants her to walk. He wants her to talk. He always asks me, ‘When she’s going to talk? When is she going to walk?’ “

“I’m like, ‘Well now she’s walking.’ [Then he asks]: ‘When is she going to talk?’ Sharing is not his favorite word,” adds Sims, who’s also getting ready to celebrate her little man’s fourth birthday with a “big Lego party.”

RELATED VIDEO: Molly Sims Opens Up About the Routine That Makes You Want to Workout

“He’s very excited and I have an awesome cake,” says Sims, 43. As for daughter Scarlett, she’s “cutting four teeth this week.”

“We’re very sassy,” adds Sims. “She might become an early biter. I’m just saying. She’s like a cat when she bites.”

And when it comes to squeezing in time for herself, the mom of two uses her little ones’ nap time to fit in workouts.

“That’s my ‘me’ time,” says the model and actress. “Nap time equals ‘me’ time, and it’s very important.”

RELATED VIDEO: What’s a ‘Snake Arch?’ Molly Sims & Trainer Nicole Winhoffer Demonstrate the Fitness Move You Need to Know

Sims – who works with trainer Nicole Winhoffer when she’s in New York and does Body by Simone while in L.A – says she enjoys “doing a little bit of everything” when it comes to her fitness routine.

“I really try to mix it up,” shares Sims, who stunned at the event in a MaxMara bodysuit – the first one, she reveals, “since I think before I gave birth like many, many years ago.”

She adds: “I think for me because I’ve done so many different things, my body needs it. I need to hike one day, run one day, do Body by Simone one day … get down and do some burpees. It’s weird. I do better when I don’t do the same thing three or four days in a row.”

— Mariah Haas