She would always say, "Don't argue with the designated driver". Rose quoted Shareen's statement after journeying with the Ninth Doctor to Platform One in the year 5.5/Apple/26. (TV: The End of the World)
Before Rose left her home planet of Earth with the Ninth Doctor on 6 March 2005, Shareen had been upset and Rose had tried to comfort her, spending at least one night at Shareen's in her effort to do so. (TV: Aliens of London)
After Rose returned to Earth with the Ninth Doctor, she told him that she planned to explain her twelve hours' absence from the council flat she lived in with her mother Jackie, by telling her mother that she had spent the night at Shareen's. When she went back to her home, Rose claimed that Shareen had been "all upset again". However, as Rose had actually been away for twelve months, and not the twelve hours that the Doctor had erroneously estimated, Jackie knew better than to believe her story about having been at Shareen's. (TV: Aliens of London)
After an argument with Sarah Jane Smith, Rose cited that the only time she and Shareen "fell out" was over a man, while she and Sarah Jane were similarly fighting over the Tenth Doctor. This implied some level of friendship with her. (TV: School Reunion)
Behind the scenes
- Shareen has never appeared on Doctor Who, and has only ever been mentioned by Rose.
- In the Doctor Who Annual 2006, an article about Rose, written by Russell T Davies, includes a paragraph that gives Shareen's last name as "Costello". The paragraph details how, on a school trip to France when Rose was 13, she and Shareen, Rose's "best mate" (at least at that time), escaped the teachers who were accompanying them, crossed town, and boarded a train to Parc Asterix, instead of going to the Louvre (which they had been scheduled to visit on that day). After they were caught by police while waiting in a queue for the Menhir Express, Shareen was sent home with Rose.