If you cannot avoid confrontation today (or at any time in the future, as well) the thing to remember is that she did not cheat to hurt you. Cheating was something that she thought herself entitled to do on the side and that you'd never find out, being half-a-world away.
The difference is small, but I think important. She didn't wake up one day thinking, "How can I hurt LtCdrLost the most today?" Instead, she woke up thinking "I'm lonely" or "I can't handle the separation" or "He's being deployed on purpose to hurt me" or some equally inane drivel.
For her cheating is a coping mechanism just like your compartmentalization of the knowledge of her A was a coping mechanism. Her coping mechanisms are faulty. She wanted what she wanted and she went for it with little consideration for the fallout. If she thought of it at all she told herself that she'd get through it okay and that you'd forgive and forget. Because that is what people with bad coping mechanisms do.
You and she got M and made vows to each other. To you those vows meant a lot. To her, they didn't. Her own wants and needs trumped the vows. That is her decision, 100%. You had absolutely no say in how she reacted to the separation of deployment. She had 100% control over how she reacted to the separation of deployment.
She could have told you that she didn't understand what the separation of deployment would feel like and she's sorry but she couldn't handle it. She could have talked with you and been Open, Authentic, Trustworthy, and Honest (OATH) in her communication with you. It would have hurt like a son-of-a-bitch, but it would have been open, authentic, and honest communications. You two might have even decided to split. It would have been a decision of two parties.
Instead, her coping mechanisms don't work like that. She wanted to be a wife and do un-wifely things as well. And then she decided to do that, and that's 100% on her.
You posted earlier that you now wonder if she cheated during past deployments. This is you trying to come up with a new "personal narrative" of your life. Your "personal narrative" is your personal, internal, story of "how LtCdrLost got to where he is today". Breaking that personal narrative as she did results in intense personal mental and emotional turmoil. Remember those times when you've woken up and not known where you are? Remember the confusion (and possible light panic) when you awake thinking that you're somewhere else? You can usually work out that confusion pretty quickly as you remember how you came to be where you woke up.
Mix in those feelings with the knowledge that your person-who-has-your-back has been actively lying to you, betraying you, and you can begin to understand the frustration and rage that you now feel.
From further down the road than you are right now I can tell you that it doesn't really matter to the "now" whether or not she's cheated before. She's cheated now and that is enough. You might or might not find out with 100% certainty whether or not she's cheated before. None of that matters _now_. She's cheated, you found out, and you're done. That is a perfectly valid response to being betrayed.
It is also perfectly valid of you to want to find out whether she's cheated before. Some people need to know and some don't. Both are valid human reactions to the unknown.
Remember that any engagement with her is feeding into her ego, her need to control the situation. By engaging at all with her you're giving her a chance to spin a yarn, to lie to you to try to control the situation and, by extension, the outcome. Any engagement is to her advantage.
Even if you were to sit down, alone, in a room with her and tell her exactly what you think that's to her advantage. She gets a window into your life, your mindset, and your thoughts about her. She gets ego kibbles from that (ego kibbles are SI shorthand for little feedings of an ego, basically, any attention at all). From her point of view any attention is good attention because she thinks that some day she'll be able to engage you again and try to change your viewpoint.
Your plans to not engage with her, to avoid engagements, and then to move to the other side of the country are good plans. They provide a good means to avoid any engagements that are not legally required during a D.