Not knowing more of the specifics, I'd have to say that I agree with the above poster. Your wife sounds like she's doing a pretty impressive job of manipulating the situation.
The fact is that she cannot have it both ways. Emotion is rarely rational, so you may have to let it settle a bit before you confront it head on. But that said, your wife can't have it both ways if this is to be egalitarian in terms of everyone's feelings.
Either she can share one or both of you, or she can't. She needs to make that decision and then stick by it. That isn't to say that it won't cause feelings to flare or things to happen on any given day, but without a sane and rational basis for your relationship.. you'll be trying to balance everything off, every single day.