Luisa Ines Tudela Harris Cutting, a student at Radford University in Virginia, had taken drugs including cocaine, mushrooms, cannabis, alcohol and prescription drugs when she stabbed Alex Cannon, 20, more than 30 times at the apartment they shared.
Neighbours called police after hearing screams from the apartment at around 7.45am on January 24.
When they arrived they found Cannon had been stabbed to death. Cutting confessed to killing Alexa, and rambled and prayed as she told officers she had done drugs 'with the devil' reported the New York Post.
She also tried to repeatedly put her whole hand in her mouth.
Cutting was taken to a mental health facility for a week before being transferred to jail.
Pleading guilty to second degree murder on Monday in Radford Circuit Court, Cutting apologized to Alexa’s family in a short statement.
'There are no words for this tragedy and my heart is filled with sorrow and grief…I am so so sorry,' she said.
Alexa, who was described as loving arts and music, and Cutting, who was president of the university’s Latino Student Alliance, had been friends before moving in together.
Alexa's family said she had epilepsy and had dealt with her illness courageously.
Cutting, of Jeffersonton, was sentenced to 40 years in prison by Judge Joey Showalter to be suspended after she has been jailed for 20 years.
Cutting will be on probation for 10 years after her release and is banned from contacting Alexa’s family.
Outside court, her lawyer Blair Howard said Cutting’s drug taking and had caused her to suffer a 'psychotic episode' and that she was sincerely sorry.