At the end of the series, in Echoes, she achieves this at last and becomes an official friend of the group, She is a major recurring character.Not much is known about Sissi's family life, except that her mother is apparently still alive according to interviews with head writer Sophie Decroisette.Sissie Straus Lehman (1879-1950) was the daughter of Nathan and Lina Gutherz Straus. In 1940, Irving became the Chief Judge of the New York Court of Appeals, the highest court in New York State.
In 1967, however, when Francis was 12, Sissie was killed in a car crash.
However, she admits in Holiday in the Fog that she is gaining their attention through her mean actions towards them, showing that she is not one to be ignored despite the fact the Lyoko Warriors are forced to keep their secrets.
By doing so she is almost making enemies out of her would-be friends, instead of gaining any of their respect, much to her chagrin.
Pour sa part, elle n’y croit tout simplement plus, mais être ensemble devient un besoin viscéral, quasi vital pour tous deux.
Tous mettent Abby en garde : « Reste loin de lui, il te brisera le cœur ou il te détruira».