The 15-year-old, who cannot be named for legal reasons, skips about two-thirds of lessons at her Carmarthenshire comprehensive. When her mother was summoned to appear before Llanelli magistrates court last week, she accompanied her.
Robert Powell, the solicitor representing the girl's mother, said: "It was a complete error on the mother's part. She thought that her daughter ought to be in court.
"But, because the girl was there, we talked to her and made her appreciate the severity of the situation. She's now frightened her mother could go to prison."
The girl was made to pledge at court that she would do her best to attend school for the rest of the summer term. Her mother was found guilty, and will be sentenced on July 14.
Magistrates' chairman Lawrence Murphy, warned: "I hope the daughter is fully aware of the consequences for her mother if she refuses to go to school."
Mary Thomas, of Carmarthenshire Council lifelong learning executive, rejected suggestions that the prosecution of parents could exacerbate rather than reduce the problem.
"We have seen a great reduction in truancy in recent months," she said.
"Taking parents to court is effective and has sent a message that children simply must attend school."