mid girl 

A moderately attractive woman; an average looking female.

I'd refer to myself as a mid girl enthusiast, they're far superior.

mid girl by hazmatcat June 1, 2022

Mid-Week Girlfriend 

A girl that you only hang out with during the week because the weekends are too busy with parties.

Ya bro I totally hooked up with that chick last night because my girl is only a mid-week girlfriend

Mid-Week Girlfriend by Mighty Arrow April 17, 2010