Before you decide to file Separately, consider these:
(1) Although she may save on her student loan repayments, both you and she will likely owe more in income taxes..
(2) Income-based student loan repayment plans can last 20 years or more, and your tax situation is likely to change in the meantime.
(3) There are special issues when filing Married Separately in a Community Property State.
That being said, I believe you claim your stepchild if the he/she lives with you, although the child's other natural parent might object. However, if your natural child does not live with you, then that child's other parent must provide you with a signed Form 8332 (regardless of what the divorce decree says).
