stock up on air fresher. It is a normal human thing to fart in sleep. You probably do it but don't realize it. Grow balls and stop worrying about stuff like this.

See, what you need to learn is the Self-Dutch Oven in vengeance. Next time you let out a big 'un under the covers while she's sleeping, sneak out in such a way that still contains the gases under the blankets. Then turn the lights on. She'll throw the covers over her head to hide from the light.