It’s just fiction, according to her

In Courtney Thorne-Smith‘s debut novel, “Outside In,” the characters include a vulnerable TV star, a philandering husband and a callous mom.

None of them is plucked directly from her own life, the actress firmly insists.

“I know people are going to think it’s autobiographical,” Thorne-Smith says.

But the cad isn’t her ex-husband, and the dreadful mother is “so comically not my mom. My mom would crawl over hot coals to have lunch with me.”

Thorne-Smith, 39, whose resume includes her breakout role in “Melrose Place,” the subsequent “Ally McBeal” and her current gig opposite Jim Belushi in the ABC sitcom “According to Jim,” says she deliberately avoided writing about herself.

“I got out of autobiography because my story is, I was famous, it was hard for me, I got into therapy, I had trouble with food, I got a nutritionist,” she says, referring to the obsessive thinness of her “Ally McBeal” days. “There’s no story there.”

Instead, she wanted to create an actress adrift and alone, someone who didn’t have the supportive family and friends that got Thorne-Smith through her rough patches.

“There’s so many young women today who look so lost,” she says, without naming names (hello, Lindsay and Britney).

“They have no one around them to give them real, authentic reflection. Nowhere they can go and say, ‘I’m having a hard day,’ where someone’s not going to say, ‘Well, you have to work anyway because you’re paying my bills.’

“It seems so simple, but it’s very isolating, especially at a young age, to be famous.”

Thorne-Smith’s own life seems well-ordered. She’s awaiting not only the Sept. 18 publication of her novel, but the arrival of her first child this winter, with new husband Roger Fishman.

She’s also fitting in a seventh year of “According to Jim,” scheduled to return at midseason.

Looking barely older than when she played Alison Parker on “Melrose Place” in the 1990s, the actress with the wide-eyed gaze and ready, throaty laugh clearly relishes her circumstances – especially the prospect of parenthood.

She was lucky, at age 39, to meet “my guy,” the man with whom she wanted to have a family. She and Fishman, 46, who’s in marketing, married on New Year’s Day.

“It’s such an amazing moment for both of us, because we both sort of had to say, ‘I don’t know if this is going to happen for me.’ The fact it’s happening is just astounding,” she says.

The same could be said for Thorne-Smith’s writing career.

She’d kept journals for years and briefly turned out articles on beauty and health for magazines including Allure and Self. But she realized fiction was the right vehicle for her, and finally pursued it with encouragement from her husband and close gal pals.

“Go after your dream for an hour a day, whatever it is, whether anybody ever sees it,” she advises. “You want to write poetry, whatever it is, just do it. Give yourself that gift. It’s life-changing.”

The birthday bunch

Country singer Hank Thompson is 82. Singer-guitarist Al Jardine (Beach Boys) is 65. Actress Valerie Perrine is 64. Actor Costas Mandylor is 42. Actor Charlie Sheen is 42. Actor Nick Wechsler (“Roswell”) is 29.