| Actually I don't think this transaction is taxable in the US! It could be taxable in Mexico and be subject to Mexico's capital gains tax if any. As far as the US is concerned, the transfer of funds (into the US will be most welcomed particularily at this time) would not require any material reportable event. It is because she is moving into the US with her assets that you would not have any taxable event or consequence on the filing of your personal tax returns! | 
