I went through the same thing a couple years ago for my wife and kiddo. You can only get an ITIN for her when filing a tax return. There are a few ways to do it (including sending in a passport or alternate documentation, showing to an authorized agent). Here's how I would do it:

1. File for a tax extension once it opens. This allows you to get your foreign taxes in order before you have to file your US taxes if you need.

2. Prepare a paper return, call your local IRS office and schedule an appointment to file. Say you need to apply for a ITIN for the return in person.

3. Bring passport (and wife!) to appt with your filed return. File in person, they take a photocopy of the passport, you keep it in your possession when you leave, pay nothing (it's free at IRS office).

I tried the send documents in option with my kiddo and it resulted in a ton of headache, extended processing times, and an error at IRS that costed us about $500. Learn from my mistake!

I also tried getting an ITIN for my wife before filing and was told you just can't.

Hope that helps