Would you go over to chill with just you and the chick you just dated alone? After dark, or just hit up the bar the two of you maybe watch some movies at her place and drink and hang out? I can only imagine my girl calling me and hearing my "friend girl" laughing out loud in the background clearly drunk and being ok with it.
Socially being "friends" and actually being like good friends are two different things, I can socially be friends with alot of chicks... but when it comes down to doing stuff that friends do that they enjoy doing with one another mixing a dude and a chick together is a disaster in the making.