jamie silvonek , 14 , was charged as adult with homicide and criminal conspiracy in her mother 's stabbing death .
silvonek 's 20-year-old boyfriend , army spc. caleb barnes , is accused of stabbing teen 's mother in the neck march 15 .
` she threatened to throw me out of the house . i want her gone . ... ` just do it , ' silvonek allegedly texted barnes .
cheryl silvonek 's body was buried in shallow grave near her home in pennsylvania .
affidavit states silvonek and barnes when to a restaurant after the stabbing and then drove to walmart to buy gloves and bleach .
police found victim 's blood-soaked car submerged in a pond and traced it to silvonek family .
silvonek 's attorney said the girl tearfully told him she missed her mother and claimed she was coerced .