A man walking his dog Monday came upon the body of the 16-year-old girl in a wooded area about five miles from the Welsh town, Sky News reported.
Police were downplaying reports the 17 deaths may be linked or part of a suicide cult, the British broadcaster said.
Michael Bennett, who found the body, told The Daily Mail: "It was so shocking to find this poor young girl hanging from this tree. I feel shaken to the core by this."
Philip Walter, coroner for Bridgend and the Glamorgan valleys, said earlier this month he doubted a copycat theory connecting the suicides that began in 2007.
"I'm of the mind that there is no commonality between these deaths and preliminary investigations say the same," he said.
A task force involving police, social services, health and education officials has been named to investigate the suspected suicides.