The female cryptanalyst who worked with Turing at Bletchley Park was Joan Clarke. She joined the wartime codebreaking operation in 1940 and became one of the most important members of Hut 8, the section focused on German naval Enigma messages.
Clarke was a highly accomplished mathematician who had studied at Newnham College, Cambridge. At Bletchley Park, she worked closely with Alan Turing and other cryptanalysts to develop methods for attacking Enigma traffic. Her work helped reveal German naval communications, although the secrecy surrounding Bletchley meant that her contribution was not widely known for decades.
Clarke and Turing became close friends and were briefly engaged in 1941, but they did not marry. The film The Imitation Game dramatizes their relationship and Bletchley Park recruitment, so some cinematic details should not be treated as literal history. Clarke later worked for GCHQ and remained active in cryptanalysis.