Be honest with yourself about where and how the friendship went wrong.
Were you being excessively needy or sensitive? Had it been doomed from the start? Examine your own actions and feelings to determine how you can avoid similar mistakes in the future. Examine your ex-best friend's actions to get an idea of what type of friend to avoid. If the friendship ended naturally, with the two of you simply growing apart, ask yourself why. Did she change? Did you lose a common interest? Knowing how a friendship ended can help you learn how to preserve future friendships.
Be Prepared for Fallout
If you had mutual friends, chances are some of them will have heard about your breakup before you can tell them.
If they've heard only your ex-best friend's side of the story, you may find them cold or distant. Expect to lose some other friends as a result of your breakup as those who feel greater loyalty toward your former best friend drop you. Be prepared for the other person to take vengeful measures, such as spreading rumors or trying to ruin your reputation.
Tie Up Loose Ends
If you're going to sever contact forever, you'll need to remove all evidence of your former best friend from your life.
Return anything you borrowed from her and ask for your own things in return. Say what you need to say and leave it at that. If you had made plans together for the coming weeks, such as dinner out or a vacation together, call the restaurant or travel agent and cancel immediately. Change all of your computer and Internet passwords. The extent of the hurt determines whether you remove your former best friend from any social networking sites to which you belong. It's best to cut off all contact for a while, but if you don't want to delete your friend just yet, try simply excluding the person from the news that appears on your page.
It's natural to have a grieving period when any relationship ends, but don't overdo it.
Not all relationships are meant to be forever; if one ends, there's often a good reason for it. Focus on the negative things you're eliminating from your life rather than missing the occasional fun times you shared. Get out and meet new people as soon as possible and let friends know you're in the market for new pals. Avoid talking about your ex-best friend or sharing details about your breakup; it's no one else's business and gossiping only makes you look petty and immature.