As TurboTaxLina explained, "If this is the first time she was granted the F-1 visa, she will be considered a nonresident alien. In fact, she will be a nonresident for the next five years from 2017-2021. However, if you are a resident for tax purposes by meeting the Substantial Presence Test SPT, you can treat her as a resident by making an election of Nonresident to resident."
If you make this election, you will only be able to file by mail.
If you are filing as Married Filing Jointly and you claim an exemption for your NRA spouse, your NRA spouse will be treated as a US resident alien for US tax purposes and all of your spouse's worldwide income in USD will be subject to being taxable as a US citizen or resident alien.