Would it make a difference if she did have the abortion but is was the child of someone else with whom she had more or less simultaneous affairs?
Seems like the logical denial to me.
Possible scenario: staffer discovers she is pregnant and decides to have an abortion, but doesn't know who the father is, or the father can't afford to pay...so she has a quick fling with Corzine, then tells him a while later that she is pregnant...so he pays thinking it's his kid.