Hi Cook4Andy
First, she knows she hurt you and adding more guilt and shame will not enhance her recovery nor your own. You don't have to pretend that it all was a picnic, but at some point you have to deal with it and let it go. They say the best way to get rid of a resentment is to forgive. Works for me.
As for the boyfriend, I would sit down with her and tell her the facts if there are things she should know about him. Then let her make her own decision, right or wrong.
You don't have to walk on eggshells - she will either stay clean or relapse regardless of how you walk. But you don't have to throw the eggs at her either. Just tell it like it is and let it go.
If this reply sounds flip, I don't mean it to. I say it with love in my heart. I have been through all this with my son, who is an addict, and I know the pain of watching them destroy themselves. And the girlfriends (in his case) from Hell.
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What I learned is that it is HIS disease and HIS recovery and I have no ownership of either. Once I finally learned to let go (and to stop grabbing back on again), it got better for me and better for him.
My prayers are with you both.