Yeshiemebet Girma, 32, was the partner of Hussein Osman, one of four men who unsuccessfully tried to blow up three underground trains and a bus to replicate attacks a fortnight earlier in which suicide bombers killed 52 commuters.
The July 21 attack only failed because the men's bombs failed to explode.
The Old Bailey was told they would have caused "carnage and mass murder" had they done so.
In the chaotic aftermath of the failed bombings, Osman fled to Rome where he was eventually arrested, deported back to Britain and jailed last July for a minimum of 40 years.
"Armed with that prior knowledge of what was going to happen, the defendant Yeshi Girma could have attempted to prevent the attacks," said prosecutor Max Hill.
He said 30 minutes after the bombings went wrong, Osman had phoned Girma, the mother of three of his children, to help plan his escape.
She, along with her brother Esyas, 22, and sister Mulu, 23, helped him to escape to Brighton and then to return to London two days later.
He fled Britain ultimately for Italy on a Eurostar train on July 26, using his brother's passport.
Prosecutors said various defendants assisted Osman in different ways, from smuggling him out of London, to giving him accommodation, tending his injuries, washing his clothes, disposing of incriminating evidence and searching on the Internet to find out the state of the police investigation.
Yeshiemebet Girma said that apart from the times Osman came to visit their children at her flat she did not know where he was. She said they had never been married and she had never lived with Osman - despite them having three sons together.
However, she was convicted of having information about terrorism and "without reasonable excuse" failing to disclose it, and was also found guilty of assisting an offender.
Esyas and Mulu Girma were found guilty of assisting an offender and failing to disclose an act of terrorism. Mulu Girma's boyfriend, Mohamed Kabashi has pleaded guilty to similar charges.
