Female scribes must have existed in the past. There are confirmed cases of things exclusively used by women - glyphs, dialects, etc.
Is it possible to find a gendering in penmanship in ancient, medieval and modern history?
This is the best I know of (although for the letters signed by women, there's a chance they're dictated to a scribe, male or female). Interesting topic! http://vindolanda.csad.ox.ac.uk/
The daughter of sargon of akkad was high priesters at Ur for the moongod Nanna. Her name was Enheduanna. She was active in the cultural life in South Mesopotamia. She is credited with several literal compositions. She is The first identifiable author in world literature. Most of her corpus consists of hymns.
Parafrased from Marc Van De Mieroops 'A History of the Ancient Near East' p. 66.