It depends on what state you live in.
If you are in a community property state (Arizona,California, Idaho, Louisiana, Nevada, New Mexico,Texas, Washington and Wisconsin. Alaska are states where taxpayers can choose community property law in their marriage) she would have to file and claim half of your income as her income.
Unless there are non-tax reasons (like an impending divorce) I recommend filing a joint return. This will have a lower tax on your income, and you will qualify for a larger number of tax benefits. Married filing jointly is the most advantageous filing status, and married filing separate is almost always the least advantageous filing status.