Sina is a Tok'ra operative.
She traveled to Stargate Command to inform SG-1 of important information regarding the Goa'uld System Lord Ba'al. She informed them that Ba'al suffered a defeat at the hands of Yu and Anubis was very displeased. (SG1: "Prophecy")
She later returned to Earth to offer her expertise in mounting an attack on the Goa'uld Anubis who was rising to dominance. She provided the schematics for Anubis' mothership and injected Dr. Daniel Jackson and Jonas Quinn with the Radioactive Tok'ra isotope so they could get aboard undetected. (SG1: "Fallen")