Unfortunately, she can't. She's not in a valid marriage.
We run across this situation quite a bit among Hispanics. The men know that a marriage in front of a priest is forever, and some of them just won't make that kind of commitment.
That's the problem in a nutshell. It wouldn't be fair to her to put her in a situation that is an occasion of sin.
I keep telling her she is in better shape than me because she will have a Baptism of desire if anything happens to her. I'm an old sinner with a lot to answer for.
I would love for her husband to be interested in coming back to the Church, but he's not. No class is going to do it.
We've been through all the human attempts at solution of their marital situation. Only the Holy Spirit changes hearts, that's the ultimate truth and that's where we are at.