Her grandmother, Christine Sharp, was arrested, along with her partner Stuart Hazell. Since then. 37-year-old Mr Hazell has been charged with the schoolgirl's murder and is due to stand trial in 2013.
But today, Tia's grandmother was told by the Metropolitan Police she will face no further action.
Ms Sharp was arrested on August 10, on suspicion of murder after Tia's body was found more than a week after she went missing, wrapped in a plastic sheet at her grandmother's home in The Lindens, New Addington, Croydon, after a 100-strong police manhunt and a massive search by the local community.
Police had searched the terraced house four times before the body was found.
Ms Sharp's neighbour Paul Meehan, 39, remains on police bail after he was arrested on suspicion of assisting an offender.