Sad_but_happy is also correct -- you can use the ultimatum and let her know you will be verifying.

As sad_but_happy points out, you need to be willing to walk if she doesn't follow through.

Are you there yet?

I had this issue where W continued to talk to one of her OM's and wouldn't agree to stop.

I talked to my DB coach about the ultimatum, but ultimately realized that I wasn't ready to follow through on the "or else".

Ultimately, I improved myself, improved the relationship, and at that point W voluntarily gave up OM for good.

I agree with Sad_but_happy, you have two ways to go forward, you need to decide what's right for you.

Accuray

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