Laws vary by state, of course. In Wisconsin, according to the 1993 case State v. Neumann:
the offense of second-degree sexual assault by sexual intercourse does not require proof of intent
and therefore someone who claimed to be too drunk to know what he was doing was still guilty. Although that was a case involving adults and therefore a different statute, I think the statutes are similar enough to produce a similar result in a case involving a minor.
But even though intent isn't required, according to the 2007 case State v. Lackershire she's still be not guilty in Wisconsin. It flat out says that:
If the defendant was raped, the act of having sexual intercourse with a child does not constitute a crime.
Additionally, in your case, there was a gun to her head. Under Wisconsin law, the woman could not be guilty of statutory rape, because of this law:
(1) A threat by a person other than the actor's coconspirator which causes the actor reasonably to believe that his or her act is the only means of preventing imminent death or great bodily harm to the actor or another and which causes him or her so to act is a defense to a prosecution for any crime based on that act, except that if the prosecution is for first-degree intentional homicide, the degree of the crime is reduced to 2nd-degree intentional homicide.
The paper you link to mentions several possible defenses like coercion, and how each defense is not applicable in some states. I don't think it ever clearly establishes that there is a state where there is no defense. The example you (and the paper) give occurred in Florida. I couldn't find an applicable statute in Florida law, but that appears to be because it's in common law instead of a statute. According to the 1981 Florida case Wright v. State:
Florida has recognized the common law defense of duress as a defense to crimes other than homicide
so I don't think the woman would have been guilty under Florida law, either. The paper states that she was in fear for her life and that of her daughters, and it is extremely apparent in hindsight that her fear was reasonable.
I imagine that if the author was able to find an actual case where a victim was prosecuted under similar circumstances (or even one where the victim clearly could have been prosecuted under the law of that state) he would have used that case as his example instead. It seems that he couldn't... and that might tell you something. He probably used this example because it was sensational, but it doesn't seem that the woman was guilty under applicable law.