The story of 'Just A Girl' is presented (in 25 very short episodes) as Amy's video diary of her experiences as she is about to start secondary school. We see, from Amy's bedroom, that she likes all the things stereotypically associated with girls; her bedroom is pink and there's a One Direction poster on the wall.
In episode 3 Amy says that when she was born her dad was pleased to have a boy to take to the football.
Amy: "But mum knew I was different. She realised early on that I was born in the wrong body"
Amy doesn't explain why her mother came to that conclusion - presumably she was just concerned that her son liked 'girly' things and decided that he must therefore be a girl.
Last month the High Court in London published the Judgment in a case about a mother who was bringing up her son as a girl. Mr Justice Hayden found that the mother in question had caused her son “significant emotional harm” and awarded custody to the boy's father.