@Lost88,
You're overreacting.
Assuming you have no other possible proof of cheating (e. g. no whispered phone conversations, her being late with weird excuses for being late, or her accusing you of cheating), then chalk it up to some excitement she had during the day and leave it. And that excitement could have been seeing a sexy video or picture. Or it could even be running for the bus, as sweat can amplify lots of other smells.
And communicate with her! Not in accusatory fashion. Just ask, is everything all right between us? And listen to what she has to say. You know, like someone who actually cares about what she thinks and feels and wants. If she is dissatisfied, assume she will tell you. If she is fine, then put this truly minor 'incident' out of your mind and move on.