Per IRS, you can claim the American opportunity credit for only four tax years, you cannot claim again if you've finished your first four years of post-secondary school before the start of the year 2016.
Use the link below to verify if your wife's school qualifies. If your wife's foreign school is in the database, her school is eligible and her past undergraduate years would be counted towards the four years time span if to claim the American Opportunity Tax Credit. Therefore, she will not qualify for the American Opportunity Tax Credit for pursuing her accounting bachelor's degree in the US. However, she may still qualify for the other two kinds of education benefit, the Lifetime Learning Credit or Tuition and Fees deductions.
If her school is not in the system, it means her four years undergraduate time span has not been used up, she will then be able to claim the American Opportunity Tax Credit for her tuition and fees paid to pursue her accounting bachelor's degree in the US
https://fafsa.ed.gov/spa/fsc/#/SEARCH?locale=en_US
