Sheila Jameson was a wife of Alex Jameson.
Suspecting that he was having an affair, she hired a private investigator to spy on him, which he refused this job two days after he started, presumably because he was witnessing The Trust meeting. While investigating the dead Jaffa incident, Dr. Daniel Jackson questioned her. She gave him some photos made by the detective. (SG1: "Ex Deus Machina")