Faelyn Ritz, 18, was arrested by detectives on Monday after agreeing to have sex with two men in exchange for the fast-food meal.
After speaking to law enforcement officers, Ritz admitted to reaching an agreement with the men to swap sexual favours with them for a meal at McDonalds.
She told how she had met the 14-year-old girl through a friend but did not know her age.
She said the teenage pair had agreed to walk up and down a street to offer prostitution in exchange for food.
Ritz also revealed that she had planned to take some of the money the 14-year-old made from prostitution.
However, she said it was only when they had checked into a motel room that she discovered how young she was.
Law enforcement officials arrested Ritz and she was booked into the Tempe jail.
She also told officers that she had been working as a prostitute since the age of 15, charging $200 an hour.