What do you do when you have a friend who is extremely self involved?

i'm guessing the two of you are about 15-17yrs. old? any who... you do sound mature and hopefully your friend is mature enough to listen to you. my suggestion is to be open and honest with your friend. tell you truly look at her as a sister more so than just a best friend. then explain to her that you understand and appreciate the fact that she has a life outside of your friendship but you need to have you and her time and not so much you, her and what ever issues she's going through with her b/f. maybe in a light but honest way let her know that if she continues to ignore the fact that you need her (advice or just a listening ear) that when she starts in on the she and her b/f saga, you're either going to ignore her until she gets it and stops or you'll get with her when she can concentrate on the two of you and what's going on at the time with you two. again let her know that you're not trying to be mean or insensitive to her issues, you just can't get absorbed in all her personal issues with the b/f. maybe she doesn't realize she does it so much. but it sounds like it's bothering you so you should be heard and continue being sisters/friends. hope it helps. good luck