First, since she was a nonresident alien who elected to be treated as a resident alien, she would not be required to file an FBAR for the year she made the election. An NRA making the election is subject to the tax rules in title 26 of the IRRC, but the FBAR rules are in title 31.
So she would just start filing the FBAR for 2016 and onwards.
If she had interest income in that account (or dividends or any other worldwide income that wasn't reported), you would need to amend the return to include that income.
