Andrea Swithenbank, 28, has not contacted her family since July last year when, according to her partner, Pascal Volkmann, she ended their relationship and said she planned to hitchhike home.
The family knew nothing of her disappearance until mid-September when they received a letter from Mr Volkmann in La Conche, near Valence in southern France, asking if she had returned home safely.
"We're all worried sick," said her sister, Fran, 34, from Camden, north London. "The last time I saw her she was upset and depressed over the relationship but there is no way she would walk out and leave Aurore [her daughter].
"Even if she did, she would certainly have contacted us. We're a very close-knit family ... We have tried everything to find her, but she seems to have vanished into thin air."
Since Ms Swithenbank's disappearance, Mr Volkmann has been interviewed by local police. Her mother, step-father, four sisters and a brother have suffered from the anxiety of not knowing what has happened to her. They are divided in their hopes that she is alive and their fears that she may have been murdered.
"I can't help thinking that she may have been murdered by a driver who picked her up, but because it was two months before we knew she was missing, the police weren't called in immediately," said her sister Erica, 31, from Leicester.
"She was a wonderful mother and she adored Aurore. There is no way she would have walked out intending to leave her behind forever. Since she vanished, we have had a Christmas, my mother has had her 60th birthday and Aurore has had two birthdays. Andrea was apparently a bit depressed about the break-up of her relationship, but all those events would have meant something to her. She would have contacted us, I'm sure."
British consulate staff in Lyon have been liaising with the police and an examining magistrate, but they say there appear to be no new leads. "The examining magistrate operates in a regime of professional secrecy, so we don't know much about the investigation, other than that they are taking it very seriously," said Jeanie Labaye, the vice consul.
"Andrea was supposed to have been hitchhiking in the direction of Spain, so the Spanish police have been asked to help, and the Italian border is not far away, so the Italians have been notified too."
Fran Swithenbank has been in the region for the past three months, distributing leaflets and photographs, but no new leads have emerged. "We'll keep looking until we find her," she said. "It doesn't seem possible that someone can just vanish off the face of the earth."Reuse content