Girl 'groomed by woman'
The teenager was found at an address in Church Road, Horley, Surrey, on Tuesday, November 23.
Surrey police had been called in by officers in Cornwall where the girl lives. A spokeswoman for Surrey Police said the 35-year-old suspect was from Northern Ireland and had been arrested on suspicion of sexual assault on a minor and of grooming a minor for sex.
"She has since been released on conditional bail until a date in January."
Inquiries are continuing and the Surrey force was liaising with colleagues in Northern Ireland.