I am trying to figure out if it makes sense to file my taxes jointly with my wife if she is tax exempt. I haven't found much information on the web that deal with such situations but I heard from friends and colleagues that it may advantageous to file jointly as the Tax-exempt individual (spouse) would report 0 taxable income.
Honestly in most situations like this, I suggest filling out the forms both ways and finding out which gives you the lesser tax burden, as an individual answer would require knowing your full circumstances such as your income and deductions and credits which apply to figure out what would be best.
In many cases married filing jointly does give more opportunities to save but it is very difficult to guess in an individual case.
If you use software to file your taxes many products offer the ability to take your information and tell you the refund you would get with each filing status, which takes some of the pain out of entering everything twice.
Try both and find out for your individual circumstance.
One potential issue I see with filing jointly is that it will make her a resident alien for tax purposes. In G status, she is an "exempt individual" for being an employee of a foreign government or international organization. This means that her days in the US in that status are not counted in the Substantial Presence Test, so she doesn't pass the test, and she is a nonresident alien for tax purposes.
However, nonresident aliens cannot file jointly. To file jointly, you would have to use the Nonresident Spouse Treated as Resident election to make her a resident alien for the whole year. I don't know which specific tax treaty or provision exempts her income from US tax, but that provision might only apply to nonresident aliens, in which case making her a resident alien would get rid of her exemption. (But some tax treaty provisions apply resident aliens too, so you have to check.) Also, resident aliens are subject to US taxes on their worldwide income; I am not sure whether the tax treaty provision would also exempt her non-US income.