The teenager told a social worker that her Portuguese mother had called her "disgusting" and said she should "die", Judge Darren Howe heard.
She said her mother "made jokes about gays" and that her self-esteem was at "rock bottom".
Her mother admitted that an "altercation" had taken place but denied using violence.
Detail emerged in a written ruling by Judge Howe following a private hearing in the Family Division of the High Court in London.
The judge said he had analysed the latest round of a dispute between the teenager's separated parents.
Judge Howe said they were involved in a disagreement over whether the girl's 10-year-old brother should live with his mother in Portugal or his father in England.
He said the girl had given evidence during the litigation.