She found she couldn't get a job that didn't require flipping burgers so she didn't work. A year later, she was pregnant and this February gave birth to twins.
That's when she realized she had to go back to school to have any chance of success.
In August she enrolled in the Classic City Learning Center, an alternative high school for Clarke County students. Now married and raising two kids, she plans to graduate in a year-and-a-half and go to college.
"I wanted to be a good role model to my children," Ms. Whitley said. "My mom dropped out in ninth grade and I held that against her and I didn't want my kids to hold that against me."
According to a study released last week by the National Women's Law Center, girls are more likely to face a bleak future in Georgia than anywhere else in the country. The study found that 41 percent of Georgia's girls dropped out of school in 2003-04, ranking the state at the bottom of the 43 states studied.
And the consequences of their decision can be worse than for boys. They earn less, are more likely to go on welfare, and about one in three become teenage mothers.
"Studies suggest that barriers to high school graduation affect girls and boys in different ways and that some risk factors -- particularly those related to pregnancy and parenting -- are significantly more burdensome for female students," the study says.
Girls who are employed after they drop out earn an average of $15,500 a year -- below the national poverty line and about $9,000 a year less than male dropouts. It's not until a woman has taken some college classes that she earns as much as a male high school dropout.
The study estimates that if all dropouts around the country stayed in school in 2007, states would save more than $17 billion in Medicaid and uninsured care alone.
Almost half of Hispanic women who drop out are teenage mothers, while 34 percent of white girls and 33 percent of black girls who drop out give birth as teens. The children of those women are then more likely to drop out in the future, the study says.
"Obviously, the personal hurdles ... become even more challenging for female dropouts who have children, particularly if they have children in the immediate aftermath of dropping out," the study said.
The study recommends several steps to help keep girls in school. Districts should be willing to make special attendance and tutoring arrangements for teen parents to allow them to stay in school. It also promotes "effective" alternative high schools, especially those that make prenatal and pre-K education available to students' children.