Keep Your Friends Close...
I am a strong believer of surrounding yourself with people who have a positive influence on you, and because of this belief [and probably because of the self-fulfilling prophecy], I like to believe that the most important people in my life now are individuals who have, and will help me be my best self.
If you count yourself just as lucky and blessed as I am, then good for you! It would come as no surprise though, that someone who may have been a good friend before, has turned into a less-than-positive influence on your life; whether she's been influenced with another group of friends that has turned her into a designer whore so much so that she's racking up credit card debt, or she's putting you down for how you look, or generally, making you feel crummy when that's not what friends are supposed to do.
Sometimes, even though you want to hold on, you need to get rid of the toxic people in your life.
But how do you quit a "friendship" gracefully?
There are two ways, and it depends on how much respect you have for the person and how close you have been. The simplest way is just to turn down invitations whenever the person offers. Don't offer an explanation to why you can't attend, and wish them the best of time. Don't agree to rescheduling if you're never going to.
If you have more respect for the person and you think she or he deserves an explanation, you should talk to 'em, as intimidating as it might sound. Tell them that you care about them, but because of where you are in your life, your belief system, or their treatment of you, you think it's best they give you some space. If she or he is someone who respects you, even if they can't comprehend the situation at the moment, she or he would respect your decision and let you be.
You should also know that...
when you're about to start any relationship, it's important how you present yourself, whether it is to current friends, or people who might be potential friends. Even if you're unsure of yourself around this person or group of people, you should not morph into someone you're not.
Don’t agree to do something that makes you feel uncomfortable. Don’t state an opinion that will gain your friend’s support if it really isn’t something you believe it.
Standing behind your words and what you believe in makes it clear who you are, right from the very beginning, so it makes it easier for you to suss out which ones will accept you for you are, and those who you'd you bid farewell to at the party and never see again.