Theres two ways to go about this:

One being that you stand your ground and stick with her, BUT this requires absolute trust that she feels the same way about you as you do her. Honestly just the fact that she listened to his plea and is confused tells me she's not completely on your side.

Two give her space and time to figure out what she wants and needs in her life. Personally it sounds like she didnt have enough time to do this when they first broke up? It seems as if she was still hurt from the relationship and moved on but never really healed from it.. that is a ticking time bomb.

I think number two is the way to go, if you love her give her space and she'll realize on her own what she really wants. 2 years and now confusion is plain stupidity, he should not be a second thought in her mind at this point.