the defense petition to return jamie silvonek to the juvenile facility she was initially sent to was denied on friday .
jamie silvonek has been charged as an adult with homicide and criminal conspiracy .
her boyfriend caleb barnes , 20 , is charged with homicide .
cheryl silvonek 's body was found stabbed in a shallow grave about 50 miles northwest of philadelphia .
authorities said silvonek met barnes when she was 13 but said she was 17 .
before the killing silvonek allegedly texted barnes ` i want her gone '