Lose of a Friend

I apologize for this depressing post but I can't figure it out so I am trying to write it out to see if it makes sense. My best friend of 13 years is no longer my friend. We have spoken to each other almost every day. She was like my sister. I love her. But the last year or so she has changed a lot (some good, some bad) and our friendship has started to slip away. My husband noticed this a lot sooner than me or maybe I chose not to notice.
So, she stayed at my house a month or so ago and she arrived at about 9 pm. We went out to dinner at a local bar and chatted. We came home and she instantly went on my computer and started IMing a mutual friend for an hour while my husband and I sat in the living room. Then she closed her door and I went to bed shortly after. My husband said she finally came out and hour later and said good night. The next morning she was going to "fit in" 45 minutes for me so I didn't feel "used". I just left and hung out with my mom. I am not going to waste my time for 45 minutes if I am lucky.
I finally sent an email to her and said I couldn't believe how rude she was sitting in the room IMing while human beings are in the living room that she never sees. She apologized and we hadn't spoken until this weekend. I told her I could really care less about the rudeness but I felt that we weren't as close as we were and we didn't have much in common. She shrugged her shoulders, emotionless and said, "Well, as long as we can be cordial at group gatherings." I was shocked. She was willing to give up on our friendship that easily. So I explained again how I felt. I expected something like you nag me like my mom, we live further apart now, I have just been busy, maybe we should make plans to get together but nothing. I was so frustrated that she really had no reaction or seemed to care at all so I just said "fine, have a nice life" and walked away. I really wanted to say FU but I thought the better. Be a little more mature although I still wasn't. I just don't get it. 13 years of choice sisterhood and she had no reaction to our conversation. I just can't stop thinking about it. I'm hurt. On the childish side I went home, threw way her slippers (yes, she even had slippers at my house), took the picture off the wall she gave me, mailed her back her key and threw away a coffee mug we both had. Stuff that would remind me of her. I guess I have never gone through a breakup. I just want to know she cares too. Obviously, the conversation didn't go the way I planned. I didn't want to end our friendship. I just wanted to know she felt the lose too.