Growing up can suck.

How does one decide when to end a friendship? I thankfully haven't had to deal with this very much in my life, but it seems to be an issue now. I've known my friend (we'll call her Erica) for about ten years; for most of that time we were very close. When she was dealing with the aftermath of assault, I was the one she called, and when I had professional setbacks that put me in tears, she was there to talk me through it. My problem now is that we seem to be growing apart, and I'm not sure whether it's worth trying to fix the friendship or just let it go.

Erica is bubbly, bright, intelligent and can be very sweet, but she has always been kind of selfish and not the type to really put effort into friendships. I have almost always been the one to call her and to make arrangements to get together when I'm in town (once or twice a year, recently). She likes to talk about her work and her social dramas (especially the boyfriend(s) of the month), and often doesn't pick up on when I want or need to talk about something. Subtlety is very much not her strong suit. Nor is remembering important dates, or being anywhere within 15 minutes of when she's said she'll be.

On the other hand, I am nearly always 5 minutes early, make a point to remember and acknowledge birthdays, etc., and would rather talk about current events or entertainment than her work (which in no way relates to my interests), though gossip is usually okay. These differences have started to grate on my nerves, and over the last year or so, I've started feeling drained when I hang out with her. Also, when we had several months of no communication this year, I found that I didn't really miss her all that much. Am I an awful person for thinking this, and yet still wanting (somehow) to fix our friendship and get it back to the way it used to be?

I think one of the major issues is how busy we both are. I don't have the time or energy to chase her down for a phone call or a meetup that will ultimately end in me being frustrated and angry, and she hasn't picked up her half of the burden, either because of time constraints or just not caring. But at the same time, I have gone through a lot with this woman - I've trusted her with every secret I had, and had so many good times with her. I'd like to think there's still some good in the relationship and that it can be rescued.

Readers: what do you think? Given that I see Erica at most twice a year, is it worth the effort to salvage this friendship? Do you have any suggestions on how I should go about saving or ending it?