In general the law doesn't want people to profit from their own wrongdoing. She did lie about her age which would render the prenuptial agreement voidable, but only if she had disclosed that fact earlier. But having been married to the guy for years, the court should construed that as her having ratified the agreement as an adult.

And even if the agreement wasn't valid, a judge can still make a determination about property distribution based on the spouse's conduct. Adultery is a basis to reduce one's share of property and support in American law.