In a radio interview, the unnamed woman said Larossi Abballa, 25, became 'distanced' and 'changed friends' after jail term for recruiting jihadists.
The couple's three-year-old son survived the knife attack by a man claiming allegiance to Islamic State group and who was later killed by police.
Police said the bodies were at the foot of Vauban Fort on the French Channel island of Chausey, and suspected they had slipped while having sex.
Mother sues couple who saw her drunk son and who 'laughed at him, filmed him with a smartphone and let him leave' rather than help him.
The young couple were shot at close range as they sat at a café terrace in a southern district of the capital, the gunman escaping.
The bodies of the couple, both aged 86 and who had apparently meticulously planned their suicide, were found holding hands in their hotel room.