If my wife takes out a student loan while we are married and we get a divorce, am I responsible for paying half of her loan?
When parties file for dissolution in Washington, the court is required to make a just and equitable division of all assets and debts. A first step in doing so is determining which property and debts are separate (anything owned before marriage, or acquired by gift or inheritance during marriage) and which are community (presumed to be anything earned or incurred by either spouse during the marriage). But even though the court characterizes the property and debts, the designation of separate or community is not dispositve--everything is before the court, and it can order whatever division it deems fair considering the totality of the circumstances.
In the case of student loans, it can go either way. If you are supporting her while she is a student, and you divorce soon after she graduates, then you would likely have a strong case for allocating the debt to her alone. But if she continues to contribute to the household while she studies, or you support her but stay married afterward so that the marital community benefits from her increased earnings that were made possible by getting the education, then she might have a stronger case for splitting the debt.
If you are really concerned about being liable for her debt, you may want to consider a prenuptial or postnuptial agreement--community property is a presumption that can be overcome by a contract between the parties. It would not necessarily affect the relationship with the creditor, but it would allow you to hold her accountable if the creditor tried to collect from you. If you are thinking of going this route, you should definitely consult an attorney--there are a lot of intricacies to these types of agreements and if not properly executed they won't hold up in court.