Wow, OK. Thanks everyone for the responses. I am really putting myself in her shoes and trying to understand how she feels/felt. She agreed in September to stop all communications with the OM, and she did. I don't think she ever stopped thinking about him, even though she tried.
She argued that she has never been given a chance to be happy--her parents pulled her away at 18, now she feels stuck here with a failed marriage. Also there is the OM to consider, in a darker sense.
Letting the kids go for a whole year seems unacceptable in any case. They may love it there (i think they do), but uprooting them from their lives here and taking them there to establish roots for a year then uprooting them again seems pretty rough. And being without their dad for an entire year seems rough too--just as rough as being without their mom.