Cecile is a young woman with thick wavy brunette hair and brown eyes. A large portion of her hair is bundled into a front braid. When working as a nurse, she wears the standard pink uniform of St. Ursula's Medical College, with black tights and a pink cap. When not on duty, Cecile favours a cream coloured thick woollen jumper and a long multi-layer puce skirt with gold patterns. She also wears sandals with blue criss-crossed straps and golden bangles.
Cecile is often quiet and warm-hearted. She does her best to help all people in her capacity as a nurse. Despite holding a large amount of sadness of the loss of her partner, she feels duty-bound to look after his brother and create a warm, supportive environment.
Although a natural airhead, Cecile is an incredibly open-minded person. Thanks to her kind and caring personality, the doctors and head nurse at St. Ursula Medical College often rely on her to relay messages to patients. When Crossbell falls into chaos or panic, she never loses her cool and always looks out for all of her patients.
Cecile grew up with her parents Miles and Leyte in Bellheim Apartments with next-door neighbors Guy Bannings and his younger brother Lloyd. They immediately became very close, and spent so much time together that Cecile considered both of them part of her family. Though it took a while due to Guy's denseness for him to understand Cecile's feelings for him, he eventually became Cecile's fiancé. She also has been friends with Ilya Platiere since Sunday School.
After Guy's death and during his funeral, Cecile suppressed her sadness, put on a calm air and smiled to support Lloyd. Since she considered Lloyd as part of her family, and because Lloyd had lost the last member of his family, she felt that she had a duty to watch over him. Later on, Lloyd would cite Cecile's support as one of the key reasons that he entered the police force.
Cecile's strong devotion led to rumors among colleagues that she might be the reincarnation of St. Ursula whom the Medical College was named after. The same St. Ursula was the source of inspiration for the novel The Saint and the White Wolf. Whereas the fictional St. Ursula meets a tragic end, the saint she was based on married a knight and lived on. Zeit, who serves as the inspiration for the White Wolf in the story, told the Special Support Section that St. Ursula's descendant was still alive today and working at the hospital, implying that Cecile is actually the descendant in question.
Cecile is the best friend of Ilya Platiere and the two often hang out together and go shopping. Cecile is introduced to the Special Support Section when they visit the Medical College and meet her when she is looking after patients. Cecile is in charge of looking after Shizuku MacLaine, and goes on frequent walks with her.
When monsters attacked the Medical College during the Cult Incident in S.1204, Cecile showed her strong sense of responsibility by intending to sacrifice herself so that her patient, the young boy Mikhail, could escape.
Cecile accompanies Lloyd and the SSS for their holiday in Mishelam. She and Lloyd ring the bell at the top of the castle of Mirrors, which is supposed to grant a wish.
Now the head nurse, Cecile meets Juna Crawford and the others when they visit the medical college and see Emperor Eugent Reise Arnor III who is being treated there secretly. She and Professor Seiland are taking charge on operating on him, which they later do successfully.
Cecile witnesses the performance put on at the Arc en Ciel and praises Sully Atraid. She is later on the beach with Lloyd, KeA and Elie talking about the successful surgery when Rean asks her to take part in a drinking contest, which she accepts. Afterwards, she returns to her duties at the College, looking after the Emperor.
Cecille keeps wishing her support on the SSS and checks in on Ilya in her rehab period, visiting her at the Arc-en-Ciel theatre. She witnesses Supreme Leader Rufus Albarea take control of the city and defeat the SSS. She escapes with Lloyd to Armorica Village where she helps treat the wounded Henry MacDowell. She later returns to the Medical College to look after more patients, including the recently defeated Ilya.