You'd be surprised of two things:
A, how codependent some people can be ... so codependent in fact that, no matter WHAT you do to push her away, she'll hold on for dear life.
B, how strong some people who seem codependent can be; if you tell her you cheated and that it's over between you, she might just get angry enough to bounce back.
It's a gamble. You don't deserve to have to play daddy to her; you deserve a woman who is on your intellectual level; your level of maturity. And in my personal opinion, you need a woman who will allow you to open up; I think your girlfriend's lack of responsibility to herself, her dependence on you, keeps you from articulating your feelings ... or dealing with them. I just don't believe that a person could be 100% rational like your persona; I don't find you misogynistic like some people on this board do, but like all of us, you have your problems.
I hope everything works out for the best.