In 2002, she was the singles champion of both the Belgium and Frankfurt International Championships and a finalist at the Orange Bowl. In June 2003, she captured the prestigious French Open junior title, becoming the first player from Germany since 1957 to accomplish this feat. In July 2003, she continued her superb form and won the Apple and Eve Newsday Long Island Classic, held in Woodbury, New York. She was also an accomplished doubles player in juniors winning the French Open title and reaching the finals at Wimbledon. As a result of her tennis success in 2003, Grönefeld had achieved the junior world ranking of No. 1 in singles and doubles. She launched her professional career debut under the direction of the USA Academy and Rafael Font de Mora.