cohostess

noun

1. A female cohost.

   “Julia Meade assisted Ed as cohostess and chief product seller during and for a while after his Toast of the Town years.”

verb

1. (rare)Of a woman: To act as a joint host.

   “Erna had dragooned a reluctant Frau Ostlinger into cohostessing a lavish party at the consulate for the children of all the more prominent German-American families in New York.”