I wouldn't tell her, let her keep wondering. If you tell her she'll just be more careful, close down what she thinks is exposed, and then get comfortable in her deception again.

Let her demonstrate that she wants a relationship with you that includes full disclosure and total honesty first.

Acc

Married 18, Together 20, Now Divorced
M: 48, W: 50, D: 18, S: 16, D: 12
Bomb Dropped (EA, D): 7/13/11
Start Reconcile: 8/15/11
Bomb Dropped (EA, D): 5/1/2014 (Divorced)
In a New Relationship: 3/2015