Identified only as girl X due to her age, she had sent her co-defendant boy Y a text claiming to have given Brianna enough pills to kill her “but she didn’t die”, the trial was told on Wednesday.
The girl and boy, both aged 16, are accused of planning and carrying out the murder of their 16-year-old victim, who was stabbed 28 times in Linear Park Culcheth, near Warrington, on 11 February this year.
Jurors at Manchester Crown Court heard about messages exchanged between the defendants on 23 January this year, three weeks before Brianna’s death, when girl X’s “fascination” with Brianna “turned darker”.
In a text discussing trying to kill Brianna with an overdose, girl X wrote: “ppl already know she is depressed and s*** so nobody would get sus … I gave her some today that should have been enough to kill her … but she didn’t die”.
The two then discuss giving Brianna ibuprofen gel in a McDonald’s milkshake and boy Y says the pills girl X gave Brianna “might be slowly killing her”, the court heard.
Girl X also tells boy Y that she knows a lot about US serial killer Richard Ramirez, known as the Night Stalker, adding, “I could talk about him for like two hours, including quotes and dates of stuff.”
During the conversation, she adds: “I always fake apologies and play the victim.”
In a statement, Brianna’s mother Esther Ghey recalled an incident in the week beginning 23 January, when her daughter became violently ill in her bedroom, which saw her “rolling around in agony, screaming in pain saying ‘I think I’m going to die.’”
She said: “I recall an incident when Brianna was really sick. She appeared to be in real pain and was screaming and crying for me to help her. She’s never been like that before and never since. This was not long before she was killed.”
Her daughter was sick over the floor and was “hanging off the side of the bed” but improved over the course of the evening, with her mother putting it down to a sickness bug.
Ms Ghey said, generally, her daughter would stay in at weekends as she suffered from anxiety and did not go out on her own.
She added: “I know she would sometimes spend time with girl X after school. Brianna was always home from school before I got home from work, so I don’t know how often they spent time together.”
Other messages sent between the two defendants show they were “preoccupied” with torture, murder and death, with a handwritten plan to kill Brianna found by police in a notepad in girl X’s bedroom after her arrest.
The note said: “Meet boy Y at wooden posts 1pm. Walk down to library … bus stop.
“Wait until Brianna gets off bus then the 3 of us walk to Linear Park. Go to the pipe/tunnel area.
“I say code word to boy Y. He stabs her in the back as I stab her in the stomach. Boy Y drags the body into the area. We both cover up the area with logs etc.”
They had previously discussed killing another child, with the girl saying she had a knife like “the one that Sweeney Todd uses” and talking about “torture before killing”.
A month later girl X sent boy Y a video, an advert for an “underground” site for people who like, “rape, snuff, torture and murder”, with girl X telling him: “I love watching torture vids.”
A day later the internet browsing history on boy Y’s phone shows internet searches on various poisons, including VX nerve agents, sarin and tabun.
Both defendants, who cannot be identified because of their ages, accepted being present with Brianna at the time she was killed but both deny participating in the killing, each blaming each other.
Trial judge Ms Justice Amanda Yip told the jury that they may notice that boy Y is playing with a fidget or tangle toy, or has a crossword book with him, which experts have told her helps him concentrate, and girl X has similar devices.
She added: “Whatever helps to manage conditions I’m perfectly happy with. Whatever helps us get through the evidence, that’s helpful.”
The trial continues.