Got an email back from a French researcher today with some good news. I wrote to the Centre De Documentation Historique sur l'Algerie, who forwarded my letter to an historian who was actually born in Setif.
He knew three families called Fillon who all lived in Setif during the war, but none had anyone called "Lulu". I sent him copies of the photos I had, and suggested that:
1) Lulu was her nickname
2)The address might actually have been her brother's barracks, and not their home address.
He came back to me today and told me someone had recognised the photo, and the woman's name was actually Yvette Dequire-Fillon. No wonder we couldn't find her. Apparently she had three sons, and left Algeria in 1961, probably for Paris. Gilbert was actually her half-brother, since her father had remarried after the death of his first wife. Gilbert died in 2007 unfortunately.
It isn't clear if Yvette is still alive, but the researcher is giving me the address of one her sons (who lives in SE France), and we'll see what happens.
Edited by The_Historian, 19 March 2016 - 02:47 PM.