I think the sex/sleaze appealed as much to a male audience as a female audience. The bands were pretty much living out the wild rock star fantasy and capturing that attitude/lifestyle in their music which was exciting and kinda like escapism for the listener. That's what metal has always been about right? Escapism. Whether its dungeon & dragons, Satan and witches, battles & swords, violence & horror, or sex & sleaze, metal has always been about escaping, unlike most current rock music which is very much about politics, society and serious contemporary issues.
I think it was the obligatory soppy love ballad that was there to melt the girls' hearts.
But I think this is one of the reasons hair metal became popular unlike true metal.... it wasn't "girls metal" as you say, but it was metal that both guys and girls both widely enjoyed, whereas most metal is very much targeted only at males. You still have metal chicks but the ratio of guys/girls in the metal scene is like 8 to 1 at most gigs! Because most girls don't wanna hear about steel and strength and dungeons and dragons and battles and war and violence and Satan and stuff.
Hair metal was more universal. The guys escaped into this wild rock & roll world of sex, whiskey, Harleys, sleaze, strippers, etc... and the girls had songs about sex and love as well which they could relate to and the musicians were wild bad boy sex symbols for them.
So in my opinion it wasn't girl's metal, it was just unisex metal whereas true metal is mainly aimed at guys.