GREAT FALLS, Mont. (AP) — A 19-year-old Montana woman has pleaded guilty to felony robbery and is expected to testify against her co-defendant in the September 2016 stabbing death 18-year-old Megan Meriwether in Great Falls.

The Great Falls Tribune reports (http://gftrib.com/2xa8QRJ ) Brianna Coombs entered her plea on Tuesday before District Judge John Kutzman. The plea agreement recommends she be sentenced to 40 years in prison with 10 suspended.

Coombs says she and her boyfriend, who was 16 at the time, planned to steal marijuana from Meriwether. However, Meriwether fought back and pulled a knife. Prosecutors say Coombs' boyfriend used Meriwether's knife to kill her.

His trial is scheduled for Oct. 27.

Coombs' attorney is free to argue for a shorter sentence. She has been jailed since her arrest.

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Information from: Great Falls Tribune, http://www.greatfallstribune.com