Megan said her pimp posted the provocative photos on Backpage.com. She had never heard of the site before and did not know how to use it, but after two months, she said, she started posting the ads for herself.
"I learned how to like, write the captions, I learned how to take the pictures," she explained. "I learned how to pay for the ad and everything, and it turned to be very, very simple."
"Nightline" obtained several of Megan's old ads, where she was listed as 19 and photographed in lingerie. Megan said the ads were typically posted three times a day; they cost $10 each and she said payment was made with an untraceable pre-paid Visa gift card that she purchased at the grocery store.
Megan said once an ad went up, the phone rang off the hook. She'd perform up to 20 or more tricks a night.
"It got to the point where I would act like I didn't hear my phone ringing because I was so exhausted," she said. "I was so-- I didn't want to do it anymore. I was in pain and I would just act like I didn't hear my phone ringing."
Megan said she was bringing in up to $4,000 a night, but wasn't allowed to keep a penny of it. If she wanted something to eat, she had to ask her pimp for permission. Then one day, he kicked Megan out, leaving her on the street in only a trench coat and no shoes. Her family rejected her calls for help and eventually the police picked her up.
"Megan's story is very typical of many girls," said Lea Benson, who heads the safe house run by StreetlightUSA, where Megan was in recovery. "When a girl is booked, we get a call immediately from either FBI or the vice [squad] that says, 'We've got a girl, are you guys ready to take her?'"
StreetlightUSA, which is funded primarily by area churches, is one of the few facilities in the country where girls who have been sold for sex, ages 11 to 17, can come for rehabilitation. In addition to food and shelter, the girls at StreetlightUSA receive counseling, mentorship, schooling and recreational activities like art classes and yoga.
But in most cities recovery centers like StreetlightUSA just don't exist, and most girls end up in juvenile detention facilities.
Benson said that more than 50 percent of the girls at Streetlight had been trafficked on Backpage.
"What words could explain the horrific outcomes that are a result of the girls being advertised on these sites?" she asked.
She acknowledged that rehabilitation of trafficked teens is extremely challenging, and it's not infrequent that girls run away.
"Trust is an issue for the first 20 to 90 days," she said. The center struggles with funding, but, she said, they never refuse to take in a new girl.
"They come with so much trauma that the healing will be a lifetime," Benson said. "Our goal here at StreetlightUSA is to help them write a new story."
Recovery, though, is possible. Jessica, now 23, said she was also pimped on Backpage when she was underage. She described horrific physical and emotional abuse she endured under at the hands of a pimp when she was just 16.
"Every pimp has a series of rules that each girl is required to follow," she said. "There was a time where I didn't obey the rules. My pimp decided to take a potato peeler... He came, grabbed me by my throat, held me against the wall, took the potato peeler, carved it into my face.
"[He] then ate the skin and told me I'm his forever and if I ever leave, worse things will happen to me," she said.