According to Official Guinness Records,
The fastest bicycle speed in slipstream by a female is 296.009 km/h (183.931 mph), achieved by Denise Mueller-Korenek (USA) at the Bonneville Salt Flats in Utah, USA, on 16 September 2018.Not only did Denise beat the previous female record but she also bettered the current male record which stands at 268.831 km/h.
For a complete list of 2018 records, please visit 2018 Guinness Records in United States.