While I don't condone him saying her name, I do want you to step back for a moment. I was TERRIFIED when my husband and I began to reconcile that at some intimate moment I would say my ex-OM's name, especially during a sexual encounter or in my sleep! While I would tell him in the least threatening way you can find that hearing her name hurt you, please try not to dwell on it. She was a part of his life for a time, and our minds are strange places. He really may not think about her at all consciously, and then suddenly her name pops out of his mouth in his sleep. We're not in control of what our unconcious mind is sorting through nor can we know in what context the name came up.
She did not "have something you don't". It was a flaw in HIM that led him to stray, not something lacking in you! Don't allow yourself to think that way, it hurts and it's way off base.
The grass may be greener, but then again, it may also be astroturf. ~Amy C Brown