Waiting in the van was hitman Miguel Gonzalez, 39, who had been hired to kill Hayes because he was ending the relationship with Hicks after 17 years.
Gonzalez shot Hayes three times in the chest before fleeing. The victim died later that morning.
Hicks had given Gonzalez the van key the morning of the slaying while Hayes was showering, said defense attorney James Berardinelli. She knew the hitman because he worked at a neighborhood garage where she and Hayes took their cars for service, he said.
"She's accepted responsibility for what she did. She's thrown herself at the mercy of the court," said Berardinelli, referring to the fact that the plea was non-negotiated.
"Although this is a very serious crime, she has also been the victim of violent crime. We'll ask the judge to take that into consideration," the attorney added.
When sentenced on June 27 by Common Pleas Judge Glenn B. Bronson, Hicks faces the possibility of receiving a maximum sentence of 40-to-80 years in state prison.
She would have received a mandatory life-without-parole sentence if convicted of first-degree murder by a jury.
Berardinelli said he was hopeful the judge would show leniency toward Hicks because she survived a horrific attack by a former boyfriend in April 1993. During the attack, he said, Hicks was stabbed 75 times and shot seven times - with one bullet still remaining in her head.
Had Hicks' case gone to trial, witnesses would have testified that she wanted Hayes dead because he may have been abusive toward her and he wanted her to move out because he planned to marry another woman, Assistant District Attorney Gail Fairman told Bronson.
Incriminating text messages between Hicks and Gonzalez and cellphone records which disproved her alibi that she was miles away at the time of the murder, led police to arrest Hicks in July 2012.
It was never revealed what Gonzalez received in exchange for killing Hayes, Berardinelli said.
Gonzalez fled to Honduras before police could arrest him in 2012, but he was captured by the FBI Fugitive Task Force last August and brought back to Philadelphia.
He is also expected to plead guilty at his next court date on April 23, sources said.