"The Independent Group instantly has a majority of female MPs" Esther Webber,
Other than where the group of MPs is a single person (such as Caroline Lucas), has a party ever had more women MPs than men MPs before?
No, at no point has a party with more than a single MP had a majority of female MPs. (As of this writing, The Independent Group is not a political party.)
Labour has so far been closest, with 45% of its MPs elected at the 2017 election being female (Source).