Detectives in Rochester are interviewing Brittanee's friends and others from the area who traveled to Myrtle Beach last week.
Allanna Lippa, 19, said she was one of about 15 people in the group who stayed "in one big room" at the motel. Lippa returned to Rochester, where she is now worrying about her friend.
"There's a million things that could have possibly happened to her," said Lippa, 19. "She was fun, a little ball of energy. But she was also depressed."
Brittanee Drexel has blue eyes and shoulder-length brown hair with blond highlights. She's 5 feet tall, weighs about 103 pounds and was last seen wearing a multi-colored shirt, black shorts and flip-flops.
Those with any information are asked to call Myrtle Beach Police at (843) 918-1300, 1-800-CRIME-TV or 1-800-THE-LOST (843-5678).