In general, are there precedents that show that Russian law will honor a foreign/American pre-nup if that is what the parties agreed to do when they got married and signed it? Does it matter that the document was not done in Russian if I can prove she understood what she signed?
It does not matter for the court that the agreement was signed only in English – it is not a problem to translate it and understand it. For the court it is important that the parties signed the agreement and put their signatures with their own free will. The contract was concluded and registered abroad on the language of the country where it was concluded. The attention will be paid the form of the agreement, if for the contract it is necessary notarized form of the agreement, then the simple written form will not be accepted by the court.
As for the essence of the agreement, it has to respond to the requirements of Russian law. First and it is important, Russian contract can regulate only property relationship between spouses. Items of the agreement which are not under the requirements of Russian Federation, will not be accepted by the Russian court.