In Australia we've had a handful of them:
In the mid-80s there was a female co-host (as opposed to hostess) on It's a Knockout (think Gladiators set at a circus), when Fiona McDonald hosted it with Billy J Smith
There's was also a kids' game show called Guess What in the early 90s. It's kinda grey as to whether the women on this show (first Alison Brahe, Cameron Daddo's wife; then Jacqui Rindt, his brother Andrew's wife) would be billed as "hosts" or "co-hosts". It was a show where a cartoonist (male) would draw pictures on a white board and the contestants had to guess what the picture was. He did a lot of talking, bantering with the female host, so he was pretty much billed as "host" as well.
Australia's first female game show (solo) host was Sofie Formica, who took over hosting on Now You See It in the 1990s.
Since then we've had Lisa Trealor on I Do I Do, Cornelia Frances on The Weakest Link, Kerri-Anne Kennerley on Greed and Simone Kessell on Dog Eat Dog.
Also, in the mid-90's there was a kids' game show called Challenger which had a female co-host, Zoe Sheridan