We have all a better guide in ourselves, if we would attend to it, than any other person can be.
--Jane Austen in Mansfield Park
Giving advice would be much easier if I kept it to the bare essentials: go with your gut. It rarely leads you astray. More often, when you're getting off-course it's because you've thought everything through too deeply. Go back to the beginning--what was your first instinct? That is usually the correct one.
But since you've taken the time to write out a detailed letter, it feels only right to provide a detailed response going through the whats and whys of it all. But here's the problem with giving advice--I'm limited to the information you've given me. I don't know if your friend is someone you met a few days ago or has been in your life since kindergarten. I don't know if she is part of a larger circle of friends or if she could be excised from your life easily. And, most importantly, I don't know all the complex emotions that go into painting the larger picture of how you feel about her. Has there always been something about her that has grated on you or are you confused because until this point, you've always felt that she was more like a sister. I just don't know.
It comes down to the fact that while I'm proficient in general social codes, I'm not fluent in the unique idioms of your life. Even if I spent every single day with you and you told me everything you thought and felt, I would still never know you as well as you know yourself.
Therefore, here is the key to take away from all of this: another person's advice is only as good as how much it speaks to you. In Mommies, Daddies, Donors and Surrogates, Diane Ehrensaft quotes Flight of the Stork author Anne Bernstein, "as you cut the suit to fit your body and not your body to fit the suit, take expert advice only when it fits." Therefore, if my advice goes against what your heart was telling you to do when you wrote me the question, go with your heart.
Then why even ask for advice? To get confirmation that you're on the right track, to gather ideas on how to approach a problem you already know you need to tackle, to hear how an outsider sees your situation. And sometimes, your heart is simply whispering too softly and it's impossible to hear the message your gut is trying to send. Those are the times when hearing another person's words can help you form your own and send you on your way towards a solution or peaceful acceptance.