The mother of a Connecticut teenager stabbed to death at her school has offered to settle lawsuit allegations against the city of Milford and its school district for $23 million.

Lawyers for Donna Cimarelli-Sanchez filed the offer Wednesday in Milford Superior Court. A lawyer for the city did not immediately return a message seeking comment Thursday.

Maren Sanchez, 16, was killed at Jonathan Law High School in April 2014, on the day of her junior prom. Police said her classmate, Christopher Plaskon, was upset that Sanchez had rejected his prom invitation. Plaskon's lawyer has denied the slaying was related to the prom, but he has not elaborated.

Plaskon, now 20, was sentenced to 25 years in prison last year after pleading no contest to a murder charge.

Cimarelli-Sanchez filed a wrongful death lawsuit against Plaskon, his parents, the city and the school district last year. Plaskon and his parents recently agreed to settle the lawsuit allegations against them for $1.6 million — an amount that awaits court approval.

The lawsuit alleges Plaskon's parents and school officials could have prevented the killing by taking appropriate steps to address his mental illness. Plaskon's parents and city officials filed court documents denying wrongdoing.

Plaskon's parents told authorities that he had possible depression, suicidal tendencies, self-mutilating behavior and mood swings. Other court documents said Plaskon heard voices in his head that made him kill the girl.

The attack happened in a first-floor hallway at about 7:15 a.m. Students described an emotional scene where people were crying as police and paramedics swarmed the school.

A witness tried to pull Plaskon off Sanchez during the attack, and another saw Plaskon discard a bloody knife, according to an arrest warrant affidavit. Plaskon was taken to the principal's office in bloody clothing and told police, "I did it. Just arrest me," according to the affidavit.

In the court documents filed Wednesday, Cimarelli-Sanchez offered to settle the allegations against the Board of Education for $15 million and the city for $8 million.

"The offers of compromise that have been filed reflect what we feel are fair numbers for Maren Sanchez's terrible death," said David Golub, an attorney for Cimarelli-Sanchez.