Interesting way I handled the whole "Do you mind if I bring a friend with?" question from girls before meeting up with you..
Girl - 40 mins later: Hey do u mind if I bring my friend with?
Me - 7 mins later: Ya. Thats stupid
Girl: Why is that stupid?
Me: Uh no. This isnt kindergarten. Totally lame I hope youre not serious lol
Girl - 1 min later: Oh god...calm down! It was just a question. Dont get urself all in a tizzy
Me - 1 min later: Aight let me know quick Im ready to bail on this whole thing. I mean thats so weird to me. I want to hang out but Im not here to babysit
Me - 7 mins later: Pumpkin!! Ok no tizzy. When you coming
Girl - 1 min later: Im leaving in 30 mins but let me kno if u still want me to come
Me: I do babe. K see you soon
Girl - 1 min later: Ok
Funny enough I have handled the extra friend SO often it doesn't even bother me anymore. Either they sit in the living room and listen to their friend/cousin/coworker get banged in the other room or they join in. This was several years ago but damn I cut it off hardcore, lol. Anyway she came over without the friend and got banged.