You were mad because she went behind your back. It violated your trust. Trust is a huge factor in these types of relationships. She may have told you she’d never cheat again, but maybe she’s just extra careful not to get caught again. I’d say you start the conversation by telling her you have something important on your mind that you need to talk about. Tell her you’ve thought a lot about her infidelity and how it’s affected your trust. She can regain that trust by being 100% honest... always. Then segue into how you’ve come to terms with it. If talking about it turns you on, let her see how much it turns you on.