Decluttering "Friends"

In college I developed a very close friendship with a girl in the dorm and we even joined the same sorority.
We soon became best friends.
Slowly she began to trust me and divulge information and problems and she became needier and needier of my time.
She had some serious mental issues and only as an adult did I realize she should have been in therapy. (child of alcoholic, abused by brother, cutter, bulemic, manic-depressive - yes it was diagnosed).

Another girl in the sorority (her little sister) and I used to talk about how she completely drained us but we felt obligated to help her. Who doesn't want to help someone in need who asks for help? I actually thought it was kind of cool to have a friend so screwed up. Maybe it made me feel better about myself.
But happened over and over and over again - she would come to us for advice and to talk about her problems - and was sapping us. And it wasn't any fun.

Eventually, an attempted suicide drove us away completely. It was the kind where you knew it was a cry for help because she called us after downing a bottle of pills.
When I graduated and moved away, I soon realized that being away from her gave me energy. When she tried to keep up the friendship, I kept her at an arms distance, didn't return phone calls, etc.

It taught me alot that would come in handy in my future adult life about the type of people I want to be around and the type to avoid.

Now as a professional organizer, I call this decluttering people in my life. These are the people who drain you. These are the people who don't support your ideas and dreams. These people cut you down to make themselves feel better.
I have decluttered boyfriends and others by using simple clear language such as: I don't think this is working for me.
I didn't even try to say "let's be friends".
I have even de-cluttered my draining relatives.
Email has helped a lot because I can converse when it is convenient for me, keep conversations short, and I don't get so emotional. If I receive an email that sets me off and hits hot buttons, I can write a response to "vent", and then delete it and instead send something less harsh.