I don't believe that trying to share her pain is the way to go. It isn't possible, and what's the point? If you're talking about empathy, that's another story. Validating her feelings, affirming them, acknowledging them...there's a difference.
Feeling the other's pain is not going to help ease hers, and if it was a valid way of fixing all of this, there wouldn't be any madhatters. My H cheated on me a long time ago, I felt his pain as a BS, and I cheated on him years later anyway.
IMO, the way you help fix this and help her heal is by being completely transparent, humble and kind, work on yourself to figure out what is wrong inside you. Work together as a couple trying to fix the foundation, and when she doesn't have it in her to do that, you do it anyway.
That's how you help ease her pain, IMO.