She was born in Darmstadt. After her mother's early death, she was sent to the Kaiserin-Augusta-Stift, a very strict boarding school in Potsdam. In this institution, the girls of the aristocracy were drilled to learn discipline and submission. After leaving school, she married Baron Ludwig Hatvany (1880-1961), a rich Hungarian writer and landowner.
While married to Hatvany, Winsloe wrote Das Mädchen Manuela ("The Child Manuela"), a short novel based on her experiences at Kaiserin-Augusta. Soon after, her marriage broke up, but Hatvany made her a generous allowance after their divorce. That novel was released in 1933.
Winsloe was involved in a relationship with newspaper reporter Dorothy Thompson, probably before World War II when Thompson was reporting from Berlin.
Winsloe then wrote the stage play Gestern und heute (literally "Yesterday and Today").
The original title was rejected as too insipid, so the play was renamed Ritter Nérestan (literally: "Knight Nérestan") when it appeared in 1930 in Leipzig. When it was brought to Berlin, it was renamed again to Krankheit der Liebe (lit. "Sickness of Love").
In 1932, her play was performed as "Children in Uniform" (English adaptation by Barbara Burnham) at the Duchess Theatre in London with Cathleen Nesbitt and Jessica Tandy in the cast.
The play's success led to the production of the film Mädchen in Uniform (1931); Winsloe was one of the screenwriters. Mädchen in Uniform was a considerable success, both financially and critically. This was due to its ambitiously aesthetic form and the fact that only women performed in it. The lesbian aspect of the story was downplayed and depicted as an adolescent crush, even though Winsloe co-authored the script, and Leontine Sagan, who in the play had stressed the lesbian aspect, acted as director.
The play ends differently from the film. In the play, the young student, Manuela, is destroyed because of rejection by her teacher, Fräulein Elizabeth von Bernburg, who did not dare to side with Manuela against the headmistress or oppose the brutal educational methods. Manuela commits suicide. The film is more ambiguous, with von Bernburg attempting to defend the student and herself. Christa Winsloe may be recorded as having written the first detailed play on lesbianism in the Weimar Republic.
On the strength of the play's acclaim, Winsloe moved to Berlin, where there was a lesbian sub-culture. She had plenty of money (from her ex-husband's allowance), worked as an animal sculptor, and had a wide circle of friends. She was a member of the SPD (the German Social Democrats, then largely reform Marxist in orientation), and was open about her sexuality.
She moved to France in the late 1930s, fleeing the Nazis. During World War II, she joined the French Resistance. Contrary to what is often stated, she was not executed by the Nazis. Instead, on June 10, 1944, Winsloe and her French partner, Simone Gentet, were shot and killed by four Frenchmen in a forest near the country town of Cluny. The men said that they had thought the women were Nazi spies, and were later acquitted of murder.Winsloe, Christa, 1999: Mädchen in Uniform (reissue), Daphne Verlag ISBN 3-89137-033-4