How can I explain to my friend, she hurts my feelings when she never wants to see that side?

Okay, I have this long time friend of 7 years, and lately I have been branching out to find new friends, posting on "Facebook" and talking to her about the situation every now and then. Well I was honest and told her she has been hurting my feelings a lot lately, and I would like to figure out why so. Unfortunately, she wants to carry on about a new beaux in her life as well as her sex life. Granted mines in the dumps, but, I'm making it through and not bothering her with it. So when I bring up "you are hurting my feelings, and I do have problems too, I could use a little help in sorting them out" Immediately she flies off the handle with "Oh your saying my problems aren't as bad as yours, are you trying to say I'm a bad friend??" after that instance I let things be and carried on with my life. Well now I'm being a "bad friend" and getting scolded for it. So at a last attempt to show I'm not being a bad friend and trying to work on my issues and life. I invited her to a 4th of July Celebration. Last year she had a good time, and she was more at ease then. This year after the fighting the bickering and hub bub, she asks me if I would be upset if she didn't come to the 4th of July Celebrations, because she was offered a free trip to Chicago. Well I was honest again and said "Of course I would be upset, I asked you months ago" however I was peaceful about it and said "Well once again my feelings are hurt, but, I'll get over it. Have Fun!!" since that she has not texted me back. So as usual, I have to be the one to give in. Other friends have told me she's not being much of a friend being so self-centered, which from their point of view that's all they see majority of the time. So I remain true and still invite her anyhow, not listening to the hub bub about her always being self-centered. I try to believe the best in her, and try to make exceptions. However I'm beginning to see that I need to draw the line somewhere, but, where???? If I don't sit and listen to her ramble for about 30 minutes to 4 hours about her problems I'm a bad friend, if I set out to find other friends and get the urge to hang out with them and not her I'm a bad friend. If I try to tell her about my problems and ask for her help with them, then I'm just plain annoying. When I don't invite her to parties, which I know she's going to bow out gracefully when something better comes up, I'm being rude and uncaring. It's almost like I'm just being tolerated. If I try to end the friendship she gets up set, if I take time out and take a breather and not text her for awhile or call her, then I'm ignoring her and being a self-centered snit. So I completely don't understand anymore, and need some serious help with the situation. Thanks in advance for any insight.