Too Young for Hollywood?

With skyrocketing ratings, fanatic fans and now, a sold-out concert tour for its leading lady, Miley Cyrus, "Hannah Montana" has been a tween's dream come true — not just for Cyrus, but also for her co-star Emily Osment, who plays Hannah's best friend, Lily.

"It didn't hit me until I did a signing back in Pennsylvania," Emily said, "and there were 7,000 people waiting outside the mall."

The sister of Oscar-nominated "Sixth Sense" actor Haley Joel Osment, 15-year-old Emily got her big break after a decade of work as a child actress. She did a guest spot on "Friends" and appeared as Gertie Giggles in the hit "Spy Kids 2." Back then, she was a public school kid, living without the attention and scrutiny success has now brought her.

"It's hard because you're in the limelight constantly," she said. "You have to do everything right constantly."

For all the glory, young stardom comes with sacrifices. Snarky comments on the Internet — where some people even pretend to be Emily — means the actress has to steer clear of much of the Web. She's left school and opted instead for private tutoring, so spending time with her friends takes a concerted effort. "It's a little tough, because I don't get to see my friends at school anymore," she said. "But I see them on the weekends and we hang out all the time."

It's no secret that many tales of tween stardom have had unhappy endings. Emily is coming of age at a time when young stars who rose to fame just a few years ago can now be found in rehab, family court or just … compromising positions.

Just Saying No

Emily's father, Eugene Osment, knows how important the "how young is too young" question can be, especially because his daughter is in the public eye. He finds himself doing what some showbiz parents have not: saying "no."

"I don't believe that kids should be driving at 16," he said. "I've said no to that. "

"I want to drive," Emily said, "but I'm not begging every day, 'I wanna drive, I wanna drive.'" Well, that's almost true. "I am dying to drive," Emily confessed with a laugh, "but I'm not letting him know that. If he wants to know how badly I want to drive, then he won't let me!"

"She's not going to be driving when she's 15," Eugene said. "She will start to learn to drive … and I want her to do more studying before she's actually out there free, on her own. So that was a no."

When it comes to boys, Emily and her folks agree on how young is too young. "Not till I'm 30," she said with a straight face. "See, I want to drive. I'm being good!"

"She's not going to be dating until she's 16," her father said. "She's been out with friends — and she's had boys that she's interested in — but nothing serious, and she doesn't really want it right now."

"Right now I'm just so busy," Emily said. "I have a ton of great guy friends and we just sit and play [the video game] 'Guitar Hero' for hours."

There is one substance abuse problem the Osments are battling — sugar.

"The biggest battles on 'no' is what she eats, and it isn't anything other than just the sugar," said Eugene. "Sugar around our house is a problem mostly because of me, and I'm afraid I've given that problem to her. When we stand down at the set, she'll grab at whatever has sugar sprinkled on it in the morning."

'Busy Is Great!'

Emily's sweet tooth even factored into an upcoming "Hannah Montana" plotline. "We just did an episode where Mitchell [Musso], who plays Oliver, has diabetes and he can't have any sugar — and I was forced to eat anything he even looks at," she says. "So all day I was shoving cupcakes in my mouth and the chocolate fountain, and strawberry chocolates with sugar. It was crazy. I had so much sugar that night! So I had a rough night."

Sugar, dating, driving …b y setting those boundaries for Emily, even as some of her friends get to do things she can't, it's possible that Eugene is helping Emily avoid the more serious pitfalls of showbiz teens. "I've never had to tell her no to drugs or alcohol," he said. "She knows better. Perhaps she does know that there are already boundaries set."

There are no limits on her energy, though: Emily goes Goth in a newly released DVD of R.L. Stine's "The Haunting Hour," for which she just recorded her first music video, and she will star in a movie for the Disney Channel. For Emily, you can't be too young to enjoy a fully scheduled life.

"I wouldn't want to be at home and just sitting and doing nothing," she said.

She was reminded that nearly every teenager in America is sitting at home and doing nothing — by choice!

"Yeah," Emily said with a grin, "and that's why they need to realize that I'm so happy 'cause I've got stuff lined up every single day until next spring, basically. And that involves friends and that involves work and school and anything."

"I love being busy. Busy is great!"

"Hannah Montana" airs on The Disney Channel, owned, like ABC News, by the Walt Disney Co.