(Yes, she betrayed you with a kiss. It's probably as close to God as you've ever been.)
The silence lay warm and trembling between them, their eyes fixed on each other in the half-light. He might have left, but her voice lured him back, some murmur meant to break the quiet, tempt him into staying a few minutes more. He smiled at her. From there, it was inevitable.
Her laughter was nervous, but he responded with some joke that calmed, comforted. The words did not matter. She reached across the seat for no reason you'd understand, lifted his hair away from his face. He mirrored her, his hand warm on her neck, caught between the awkward position and the pounding desire to touch.
There was small talk, of course; there always is. But the fragile distance between them was so easily broken; his touch barely hinted at an invitation, and she met him halfway, aching for him as she did for you, once.
Their kissing was passionate; she drew the faint taste of smoke from his mouth, swallowed it as tenderly as Communion. Her fingers slid along the curve of his jaw, found it a sharper angle than yours. Some small sound escaped her mouth, perhaps a sigh of satisfaction.
You might have laughed at her: he sampled her, ran his tongue along her glossy bottom lip. He blew warm breath into her ear. When she offered her neck to him he took the gift with a teasing edge of teeth and tongue; he brushed his mouth over her knuckles, gave her Eskimo kisses until she laughed. He memorized her as you did once, recognized the touches that bowed her back and caught her breath. Each bit of his attention helped to fill a wound that you made.
Would you be jealous? No: a sense of something lost, perhaps, a favorite toy stolen by someone else. You would keep her, but you could no longer be satisfied with her – hungry for what should be yours, knowing she is rich with another man's aftertaste.
(So her kiss betrayed you – so what? You crucified her long ago.)