The former N-Dubz star, of Friern Barnet, north London, is charged with helping an undercover reporter obtain 0.5oz (13.9g) of the Class A drug for £860.
The 25-year-old singer is said to have told The Sun on Sunday's undercover reporter Mazher Mahmood, dubbed the "fake sheikh", that she could arrange for him to buy cocaine.
Contostavlos denies being concerned with the supply of 0.5oz (13.9g) of cocaine to Mahmood between May 20 and May 24 last year but she has not entered a formal plea at court.
Wearing black skinny jeans, stiletto heels, a black polo neck top and matching black blazer with her brown hair piled high in a bun, she spoke only to confirm her name at Southwark Crown Court.
She appeared alongside rapper Mike GLC, also known as Michael Coombs, 35, of Enfield, north London, for a plea and case management hearing.
Coombs, who also spoke only to confirm his name, denies a charge of supplying the drug on May 23 last year at the upmarket Dorchester Hotel in Central London.
Contostavlos and Coombs, who sat in the dock flanked by a uniformed officer, are due to stand trial on July 14.
They were bailed to return to Southwark Crown Court on June 25 when a three- day legal argument hearing will take place.
Judge Alistair McCreath told the pair: "You are both free to go. If you want to come on any further application you may do so.
"You must come on 25 June when I'll deal with pre-trial matters.
"You may both go on unconditional bail."
Contostavlos was officially dropped as a judge on the ITV talent show X Factor days before her arrest on June 4 last year, with Sharon Osbourne returning to the show in her place.