Krsytal Lee pleaded guilty to tampering with physical evidence in the case.

The ex-girlfriend of a Colorado man who murdered his fiancee is set to be sentenced Tuesday for helping dispose of evidence in the gruesome crime.

Patrick Frazee was found guilty in November of killing his missing fiancee, Kelsey Berreth. He was sentenced to life without parole plus 156 years.

The star witness against Frazee during the dramatic trial was his ex-girlfriend with whom he later had an affair, Krystal Lee, who told the jury that Frazee called her to come to Berreth’s house to clean up the crime scene.

Lee testified that Frazee beat the mother of his child to death with a baseball bat on Thanksgiving Day 2018 while the couple’s 1-year-old daughter sat in a back room.

“I saw blood all over the floor and blood all over the wall… on the floor there were bloody footprints,” she testified.

Lee also admitted to disposing of Berreth’s phone. She pleaded guilty to tampering with physical evidence.

In court in November, Berreth’s mother, Cheryl Berreth, called Lee “an active participant in the murder — the only thing she didn’t do was swing the bat.”

“She chose to cover up the murder, only speaking out to save herself. She chose to clean up the mess,” Cheryl Berreth said. “We have seen no remorse for anything other than getting caught.”

Lee is due in court Tuesday morning. She could be sentenced to up to three years behind bars.

Kelsey Berreth’s body was never found.