PHILADELPHIA (CBS) — The mother of a missing 16-year-old Allentown girl is pleading for her safe return tonight.

Sixteen-year-old Amy Yu, who was reported missing last Monday when she left school on her own volition, is still missing as of Monday, March 12.

Amy is believed to be traveling with 45-year-old Kevin Esterly — a family friend who frequently hosted Amy on family vacations.

“That’s why we’re working this hard. We have a family who has a 16-year-old girl, no matter why she left the area. We have this family who still doesn’t have answers,” Allentown Assistant Police Chief William Reinik.

Amy’s mother Mui Luu, who did not want to show her face on camera, says she “feels betrayed.”

Luu found out on Feb. 9 that Amy had lied by listing Esterly as her stepfather on school records.

Allentown Police Searching For Missing Teen Girl, Man

According to a police affidavit, Esterly signed Amy out of Lehigh Valley Academy Regional Charter School ten times between November and February without her mother’s permission.

“We have been working closely with the police and Amy’s family since February 9 and are providing whatever information and assistance we can to assist them,” said Susan Mauser, the school’s CEO.

Luu says she also found text messages that suggested Esterly was romantically involved with her daughter, who at 16, is at the age of consent in Pennsylvania.

Esterly’s wife told investigators he withdrew about $4,000 from his wife’s bank account that same day.

Police suspect the two of them are traveling together in Esterly’s red Honda Accord with Pennsylvania plates.

On “CBS This Morning,” Luu had this message for her daughter, “I want to tell her — Amy, can you come back to me? I love you. I just hope you come back.”

Prosecutors have charged Esterly with interference of custody of children and police say the car may still be in the area which is key.

If you see the car or either Amy Yu or Kevin Esterly, give Allentown police a call at 610-437-7753.

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