I am at a loss for words. You are NEVER supposed to claim citizenship if you are not a US citizen. Never ever ever claim citizenship.

If she kept quiet about it on her naturalization, no one would notice or care, however since she decided to put yes on one of the many boxes you're supposed to answer NO.

There is nothing that can be done for her, unless immigration reform were to waive the false claim of citizenship inadmissibility, or you got Obama to pardon her for that. There is no waiver for this available.