Sandy made her debut as a professional in July 2000, aged 14, at an ITF tournament in Jakarta.

In 2003, she and her partner Septi Mende reached the quarterfinals of the junior doubles competition at the Australian Open.

At the 2007 Southeast Asian Games, Gumulya won the gold medal in the women's single competitions, and also won the silver medal in the women's doubles competition with Romana Tedjakusuma as partner.

In March 2009, Gumulya retired during the second set of the quarterfinal of the ASB Pro tournament at Hamilton, New Zealand, due to a knee injury.

The injury forced her to withdraw from the third and final tournament of the ASB Pro Circuit, that at Wellington.