Vanessa Marcil wants to make something absolutely clear: She’s a nice girl. Really! It’s just her characters, she says, that are bad.

“Because I’m this dark-haired, curvy girl, I’ve always been cast in roles where I’m the bad girl or the scandalous girl,” Marcil says. “But in my real life, I’m kind of nerdy and dorky and I’m a bookworm and a homebody.”

So it’s a refreshing change, the former “General Hospital”/“ Beverly Hills 90210”/“Las Vegas” beauty says, that she can at last explore her good side on-screen in “The Nanny Express,” a Hallmark Channel original movie premiering at 9 p. m. Saturday.

Marcil plays Kate Hewitt, who takes over as nanny to a couple of precocious kids who have driven away all of their other nannies. Kate, however, is up to the challenge. Not only does she win over the children, but she also strikes up a romance with their widowed father (played by Brennan Elliott).

“She’s a hard-working, sweet, honest girl who’s studying to become a teacher and taking care of a sick father,” Marcil says. “I loved this character so much, because she’s very different from any I’ve ever played. She is just so, so sweet to the core and wants so much to do the right thing.

“Believe it or not, I’ve never played a character like that before. It’s funny. My boyfriend always says of me [much like the Jessica Rabbit character of “Who Framed Roger Rabbit’], ‘Oh, you’re just drawn bad!’ ”

That said, it’s a bit of a puzzler to Marcil that she is seen in that light.

“I never had steamy love scenes,” she says. “I started out on a soap opera when I was a kid. We were in high school. We were going to go to the prom. We never had to be in lingerie. The most they ever showed of me when I was on a daytime show was my bare back.

“And then, amazingly, on all the prime-time shows I’ve done, I’ve never been in my underwear. I’ve never done anything like that on TV. The truth is I’m actually kind of comically conservative in my life and in most of my work.”

Another thing Marcil loves about “The Nanny Express” is that, although the movie could have been just a conventional piece of family-comedy fluff, there are some surprising moments, particularly with her and Dean Stockwell (who plays her dying father) that give the film some heft. “Dean was amazing in this,” she says. “You would never guess it, but we definitely touch on some deep issues.”

That storyline involving a dying loved one packed quite a wallop for Marcil, in fact. At the end of every day, after filming those emotional scenes, she wanted to go back home and give her 6-year-old son Kassius a big hug, just to remind him how precious he is to her.

“I’m already the type of person who tries to stay conscious of that,” Marcil says. “I have a Grateful List and I always try to stay mindful of the people and things I’m grateful to have in my life. So it’s kind of hard not to be affected at the end of the day by material like this.”

Maybe her performance in “The Nanny Express” will lead to other good-girl roles, but Marcil won’t vehemently object if she’s asked to stay the vixen. After all, she points out, she’s elated just that she gets to act for a living and that she gets to enjoy the life she has.

“I grew up in the desert,” Marcil says. “We didn’t have any money. To me, it’s like I’ve won the lottery every day. I started acting when I was 5 in the theater, but becoming a professional actor was a complete, 100-percent accident. It was never my intention to do this professionally.

“So it’s kind of comical to my friends and family and my agents, all of them, that I’m not ambitious at all about my career. I don’t differentiate between levels of success, because I already have so much more than anything I ever dreamed I would have. I mean, I could be doing a dog food commercial and you’d think, from my excitement about the job, that I’d just won the lottery.”