You've really enjoyed your time as Kristen's panties. But if being a part of her wardrobe was this much fun, you can only imagine what it might be like to be a part of her body. You don't have much time to work with... if you hesitate, she'll toss you into the hamper with the rest of her dirty clothes, and you might not ever get a second chance.
Holding the image of the gun in your mind, you imagine yourself changing its settings, aiming it at yourself, and pulling the trigger.
The effect is instantaneous. You feel the cloth of your body seem to dissolve, stretching and contorting with the change. The change is quick, and leaves you stunned, much as being her panties first did. You feel the warm mounds of flesh that form your body, pulling downward and inward. You feel the warmth of Kristen's body, now your body too, and your hair all around you, neatly trimmed. The transformation worked. You're Kristen's vagina, as well as anything inside and around it.
You can see the folds of Kristen's denim skirt for a moment as she pulls it down, feel the slight stretch as she leans forward to look in curiously and determine where the panties she'd been wearing had gone. You see her face for a moment and feel her hand reach down to run itself gently around your outer edge, searching for something that isn't there. You hear her mutter something, watching as she shifts from foot to foot, looking for her panties. Eventually she gives up, and the world gets dark again. You can see a thin fabric hanging in front of you, and occasionally it brushes past you, a not at all unpleasant sensation. You feel yourself gently stretch one way and the other as she walks somewhere, then the faint light through the fabric in front of you goes out, and you feel yourself shift as Kristen gets into bed. As she does so, you feel the gentle pressure of the bed below you, and it feels quite good.
As it did when you were panties, time doesn't seem to flow at quite the same speed... one minute you're pleasantly still, enjoying the feel of the cottony fabric of the nightgown, the next...
Being asleep as a vagina is even stranger than being awake. You dream of strange things... the feel of a particular pair of silk undergarments, a hot bubble-bath, and brushing up with something soft and warm... fortunately, it doesn't seem to last long. As Kristen wakes up, so do you. You stretch with her as she climbs out of bed, your head gradually clearing as she goes about picking out her clothes. What are you doing here? Your memories from the day before come flooding back as rough fabric falls loosely over you, then is quickly removed again. You see white tile in front of you, and hear the sound of rushing water. Suddenly, you feel warm water rushing down and over you, dripping onto you, and making you feel pleasantly warm. It continues a moment, then you feel something soft running gently onto you, getting you nice and clean. You occasionally seen Kristen's hands, but you're caring less and less about what she's doing, and more and more about what you're feeling, all the more content to be a rider.
Eventually, Kristen gets out of the shower, and walks back into her room to get dressed.