It depends on whether she was married or not.
If married - no citizenship.
If not married -citizenship.
Unless you find case law or a loophole that protects poor bastard baby from lying commie bigamist father.
What about no marriage and born in Kenya?
Citizenship of the child is not the issue for natural born status, it's citizenship of the parents. Married or not, if he born in Hawaii he's a citizen, but not necessarily a natural born one.