Michie/Holly are also only the second showmance to make the F3 together and the first in BBUS, with the first being Derek/Kaela in BBCAN6.
There was also Jillian and Emmett in BBCan1
Also Drew/Diane and Boogie/Erika.
Pretty sure the latter wasn't a "real" showmance, just Boogie playing the hell out of her (though neither of them seems to be a very good person). The former... I don't remember how close they were.
But yeah looks like I was wrong whoops.
There's no exact definition to what a showmance is (although Will did coin it), but I would say merely being involved romantically, whether real or not, means it's a showmance. Erika was committed to it and Boogie was somewhat invested too, even if he always would pick Will over her. ---