We would like to elect to file jointly and understand that in our case we would need to file a W-7 to obtain an ITIN. I am a US citizen and she is currently on a non-immigrant visa and have been living together abroad for the past few years. We were married towards the end of 2022, so I would like to amend my 2022 and 2023 returns as well as indicate on the 2024 return so that we are jointly filing. My question is if (once with an ITIN) would she need to file an FBAR for her individual foreign bank account (not a joint account) if it is over $10,000? And if so, would she need to file it for 2022, 2023, and 2024?
It depends!! This is a gray area that the IRS hasn't specifically addressed. In reading this FAQ sheet from the IRS, under the heading of Who Needs to Report, it says "A U.S. person is a citizen or resident of the United States or any domestic legal entity such as a partnership, corporation, limited liability company, estate or trust". Your wife does not fit any of these parameters, even if she obtains an ITIN.
If you have signing authority on her accounts however, then you would need to file an FBAR from the time you were granted signing ability. If were granted signing ability in 2022 or 2023, you would need to file an amended FBAR for those years.