One could say that by voluntarily agreeing to sex she waives that right.
If that were true, then it would not apply to cases of rape, or when the woman used birth control and it failed, or in cases when the woman simply didn't want to have a child and got pregnant on accident. All of these would make abortion 100% legal and accessible for practical reasons, simply because it would be impossible for the government to determine in a free society whether or not the woman was lying about the pregnancy being an accident.
Furthermore, even if the woman wanted to become pregnant, that does not mean that she is entering into a long-term contract - she still has the right to change her mind at any point and determine that she wants to terminate the pregnancy.
Lastly, as I briefly mentioned in a previous post, it is a bit of a stretch to extend rights to the unborn. Rights only exist in a social context - I do not adhere to the view that rights are God-given or naturally endowed. So from this perspective, it would appear that the unborn do not have any rights since they obviously do not engage in society or even exist within the "social context."
Also one could say that if the decision is hers and hers alone b/c it is her body that she and she alone should deal with the consequences. Meaning that the father of the child should not be held accountable as he has no choice in the matter other the act of agreeing to have sex. Which you already concede isnt a binding decision in taking care of a resulting child seeing as women dont have to adhere to it.
I agree that the father shouldn't be held legally responsible for a child born out of wedlock. Again, engaging in sex does note constitute entering into a long-term contract.
Though in cases of marriage or when the mother/father do make an agreement to have a child, the circumstances change, and thus the father should be held legally responsible - and at the same time the decision to terminate the pregnancy no longer is just the mother's, but also the father's. But at no point is this a decision to be made by the government.