When to Give Up

How do you really know when its time to let a friendship go? I feel so conflicted right now. The girl who is supposedly my best friend has blasted off the face of the earth in the midst of my personal turmoil. I don't expect a huge amount from my friends. I'm not a "co-dependent" friend, quite the opposite in fact. My main expectations is for friends to rally when the going gets tough sometimes you need someone to cheer you on or make you feel as if you are not worthless or useless. Typically my friends rock at this and are there to tell me how much everyone else sucks and how amazing I am and mix me a drink if the situation calls for it. Right now I just feel as if this one friend is really letting me down.

This is a girl that I have constantly tried to build up and hold up. I have always been on her side no matter what the circumstances. I've noticed a trend with her over the last year that she has become increasingly selfish and I guess this current behavior of leaving me in the cold is a by product of that. Maybe it is just that she feels that since I'm not around to prop her up all the time anymore that she does not really feel that my friendship is necessary. I just don't know what is really going on. I know that I can't salvage a friendship alone. I know that if its something to be worth saving that she has to be pitching in as well. Right now I just don't see that. I never would have really thought that our friendship would end like this with her just not giving a shit anymore and leaving it as it lay.