if both of you are U.S. citizens then you are barking up the wrong tree and there are additional facts which need to be considered:
a. Were you both U.S. citizens at the time of the marriage? Were you a U.S. citizen at the time of the marriage but not she?. Was she but not you a U.S. citizen at that time? You seem to a well-read person, so go through the Indian Penal Code. There is a whole section there for crimes committed by foreign citizens and limitations of jurisdictions of the Indian Courts. If she is also not an Indian citizen, the jurisdiction at this time would be limited. If at the time of the marriage or just before (to take care of dowry allegations) you both were U.S. citizen, then you have nothing to worry in India. In any event, the allegations if any are to be made, would be on foreign soil.
I am not saying that you have committed any crime, but procedural grounds of jurisdictional limitations would be your first line of defense.
Like in U.S., in India too, a private party cannot condone a crime. That is the sole prerogative of the Court and the Public Prosecutor (the equivalent ot the U.S. Attorney at the Federal level and the District Attorney at the state level in the U.S.). That said, some crimes in India can be "compounded" by the victim but some require Court permission for them to be compounded. You need to read on these sections in the IPC to know if DV and 498 can be compounded by her. Even if you get a consent from her on a privately signed document, absent a Court blessing, Indian or U.S., she can always claim that she was coerced into the consent and file a case anyway. A consent without Court sanction is therefore a worthless piece of paper, nothing more. So do not get too excited even if she gives you one.
With your current status as both U.S. citizens living in U.S. all along, I doubt that the Indian Courts can assert jurisdiction of any kind other than the remote possibility of the time just before your marriage if she was not a U.S. citizen and dowry is alleged. Then that would constitute the commission of a crime on a Indian citizen on Indian soil. Whether jurisdiction of Indian Courts would survive post-acceptance of U.S. citizenship is a technical detail you need to consult an expert. My gut feeling is that she is not that smart or knowledgeable. If she was, she would have approached the authorities in the U.S. to allege domestic violence and let the District Attorney pursue the case against you. It would come free of cost and really get you into a LOT of trouble. Now, the Indian Courts are going to ask why she did not file a complain there especially when no monies are required to approach the DA's office. That would be your defense too here if the case goes that far.
In general, legal expertise is hard to come by in India. You could not have got better advice from an advocate here then the one I have given you. There are some brilliant advocates practicing in High Court and the High Court Judges are ultra-brilliant almost making up for the void in the legal profession in general. There will be plenty of advocates to give you the usual run-of-the-mill advice. GOOD LUCK!!