Diane Levin, a professor of education at Wheelock College in Boston and co-author of the upcoming book, "So Sexy, So Soon," argues that the early glam trend has the potential to create problems.
"It's not that every little piece in and of itself is a problem but it may start with nail polish and going to a spa and that becomes a trajectory for feeling good about themselves," Levin said.
And, Levin added, if they don't have highlights in their hair or polish on their toes, young girls can start to feel that "something is wrong with them."
Dr. Jennifer Johnson, a specialist in adolescent medicine in Newport Beach, Calif., who treats everything from acne to eating disorders, worries about the spa trend, too.
"Manicures and pedicures are okay; that's fun … but anything beyond that, anything that puts so much focus on appearance to me is one more step in the direction of really serious problems."
Johnson adds that if moms are bringing their daughters in for treatments like eyebrow waxing, there's a not-so-subtle message being conveyed.
"That's putting daughters on notice that that's what their moms are noticing — their appearance," Johnson said.
But salon owner Tierney believes that times have changed for kids and their parents.
"I think it's just the norm," she said. "It's baby boomer parents that nurtured and took care of their children and they want their children to look good and feel good about themselves … Let's face it, today's 12-year-old is yesterday's 17-year-old. The world is different and they are more mature and they want the latest thing."
And Donna Rabb, owner of Girl Talk at The Spa, said that there's an important education component to the services she offers.
"It's about wellness and making the body and face healthier," Rabb said. "We talk to the kids about proper cleansing and we don't emphasize beauty so much as self esteem."
As for Maria and her friends, they know exactly what a spa party is all about — fun. A show of hands revealed exactly none of the girls had ever worn makeup. And only one girl admitted having highlights in her hair but "only if you count the time I sprayed my hair green after we won a soccer game."
One of Maria's friends summed the party up this way, "This is fun, it's a treat, but I know it's what's on the inside that counts. My mom told me that."
So, the kids may be all right after all.