Kellie Martin Introduces 'Sweet Surprise' Daughter Olivia James: 'She's Our Bonus Baby!'

With a 9-year-old daughter and a barn full of animals at home, Kellie Martin‘s hands were already full when she found out she was expecting her second baby, Olivia James, who was born in February.

“We really weren’t planning on having another baby,” Martin, 40, tells PEOPLE exclusively. “It was just one of those situations that this baby wanted to be here. She really is such a sweet surprise all the way around. She’s our bonus baby!”

When the actress found out she was having a girl, “I breathed a huge sigh of relief,” she says. “I know girls, so I was really, really happy to have another girl. A boy would have been a whole other thing to figure out.”

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While she was a little nervous to have a new baby at home at first, Martin credits her husband Keith Christian, 42, with helping her to adjust.

“He helps me so much and he makes me brave, because I find babies terrifying, which is probably why I put off having another one for so long!” she says.

Still, having another child at home has been a big challenge.

“It’s a huge adjustment,” says Martin. “My husband keeps saying it’s man-on-man defense. He’s got one, I’ve got one, and then we’ll switch. It’s a lot more work, but we’re seeming to manage it pretty well.”

Luckily, big sister Margaret “Maggie” Heather has been a hands-on helper with her baby sister.

“She’s so helpful,” says Martin of her 9-year-old daughter. “She loves being a big sister and she loves reading books to her. It’s really, really sweet.”

Martin also credits Maggie with coming up with Olivia’s name.

“Maggie said, ‘What about Olivia?’ I was like, ‘I love it!’ ” she says. “And I’m a huge Scandal fan. We didn’t fully name her after Olivia Pope, but I have a great affection for the character!”

The former ER and Life Goes On star says the best part about having a second child is being able to savor the moments with her newborn even more.

“I’m a calmer mom this time,” she says. “It’s hard to know that you have to kind of stop your life, and really just give yourself over to it, but if you do that, you’re so much happier.”

She adds, “I really decided that I was going to do more of that rather than fight against it, which is what I did with my first one. With this baby, I really decided I’m not going to rush my body, I’m not going to rush work, I’m just really going to take my time.”

For more from Kellie Martin, pick up the latest issue of PEOPLE, on newsstands now.

— Gabrielle Olya