There's a lot of information missing for a good answer. Sex of each of you, past relationship between all of you, who is paying or providing transportation. The importance of each of them to you. How each was invited and why the one is not now wanted. There is really no way of getting out of it without hurting their feelings to some degree. What comes after depends on the person. Accept resposiblility for the mix up, you want it to just be the two of you and perhaps you and the third person can go another time or do something else in the future. You don't have to mean this, just sound like you do. You are already screwing with them so more shouldn't matter to you.
As nicely as possible. Make sure to mention all of her good attributes that will help her get a new boyfriend quickly.
ask him/her nicely and wait patiently for an answer
Ask them nicely, but always say please
As in what??? a crush? or a friend??? As a friend??? you treat them nicely, and don`t ditch them. As a crush??? It just happens.
well tell them and don't be a jerk about it just tell them nicely.
You look him in the eye, seriously, and say "If you need a friend just to talk to - anytime - I am here for you". That will get the message across nicely.
Treat them nicely and do things that you know they would like and appreciate.
TinyUrl will do the trick nicely - tinyurl.com
tell her off nicely
If a friend is driving you crazy by calling then ask them nicely to stop calling and if they dont just turn your ringer off on your phone
A person being interviewed for a job should dress as nicely as possible, no matter the position.
Yes it is possible. But if they have a password on it just go and ask them nicely if they could let you use their internet.