I'm G-4 visa holder working for an International Organization. My wife is G-4 visa holder (Dependent). She worked for a year and received less than $17,900 as salary. We're both under 65 years. If her status is filing jointly does she must file?

What is your citizenship? You need to check what is the tax treaty.

She cannot file jointly, because if she does, your exempt income is NO LONGER exempt. NOT a good thing!!

Have her file Married Filing Separately.