We all know her, the girl who just like Lindsay Lohan seemed to go overnight from good girl to bad.

She moved from playing with Barbies to sneaking a cigarette, a beer and a French kiss, just like a lot of us once did. Except she didn't stop there.

It's normal for girls to experiment, according to Bostonbased family therapist Carleton Kendrick. But spiraling out of control is another thing, and parents have the challenge of knowing the difference.

Actress Lohan, who recently turned 21, was arrested and released on bail last month on suspicion of misdemeanor driving under the influence and with a suspended license. Cocaine allegedly was found in her possession. (She has said the cocaine was not hers). Less than two weeks earlier, she had completed her second trip to rehab.

Kendrick, who co-wrote "Take Out Your Nose Ring, Honey, We're Going to Grandma's" (Unlimited Publishing) said there are lessons to be learned from the Lohan affair, even when it comes to noncelebrity kids.

"An adolescent girl's job is to ride the roller coaster. Risky behavior is part of frankly what should be happening during adolescence," Kendrick said. "But kids tend not to spiral all of a sudden. It (Lohan's downfall) started at a particular level and got worse. And one would hope parents would be paying enough attention and know their children (well enough) to spot the signs before they were on a DUI."

Psychologist Susan Bartell said the lesson here for parents is to communicate with their kids — long before there may be a problem.

"Know who their friends are. Stay on top of them. Keep talking to them. Have all the kids over at your house," Bartell said. "In adolescence, the hard work begins."

She said parents shouldn't give kids enough rope to hang themselves, but they also shouldn't be too strict or the kids will rebel.

"You have to have a balance," Bartell said. "Know what's going on with your kid. Push them. Empathize with them. Feel your kids' pain."

Kendrick suggested parents talk to their kids about the troubled trio that is Lohan, Paris Hilton and Britney Spears.

"The conversation should not be, 'If you do that you'll end up like that girl.' It should be, 'Why do you think these young women are acting so self-destructively?' You shouldn't tear down someone your daughter admires," Kendrick said.

Bartell said the unnamed victim of bad behavior is often the bad girl's friends, who may not only be faced with being dragged along into dangerous situations but also forced to decide whether or not to tell an adult about their friend's problems.

"It's like the other side people don't really see," Bartell said, adding that she has treated girls "in mourning" over losing their best friend.

But Bartell said even if in an anonymously written letter, she encourages girls with a friend who is getting out of control to tell an adult.

"Otherwise, if something bad happens to the kid, you will feel very guilty you didn't tell," Bartell said.