Well you say she is a great girlfriend, so you get extra credit for that, but you used the word confront in describing your talk with her about it. Did you confront her as is "Why don't you want to suck my dick?", or did you go about it caringly and gently?
Communicating your needs to her is essential. You should strive to find out why she isn't into it, then ask if she would like to try to overcome her fear/aversion. It's ok for her to not like it, and you may have to just enjoy your sexual relationship with her without getting head. I don't see her as selfish at all. I think you are just a tad frustrated because you work so hard to please her and you may feel like she is not doing the same thing. That's natural and ok as well.
I personally love to give blow jobs, but it is an acquired talent and like. Ask yourself this: Is everything else about her, sexual and non-sexual, awesome enough for you to forego getting blown for the remainder of the relationship? Sex is very important for couples, but it is not the most important aspect of being together. I would rather be in a great relationship with so so sex than in a so so relationship with great sex. I can have great sex all by myself!
Perhaps you can ask her for a great hand job. Tell her how turned on you will be if she blows ya with gentle instructions from you......
Good luck!