"What did you have in mind?" you ask Brooke anxiously. You've seen that expression from her before-- it usually means she's about to do something something really crazy and impulsive.
Brooke opens the jewelry box and takes out the Body Changin Bracelet, which she tosses to you. "Since you had so much fun giving me another pair of boobs, let's see you give yourself a pair now. And while you're at it, you might as well go all the way, too. 100% X-chromosome."
You stutter as you grasp her meaning. "Y-you mean... you... want me t-to...?"
"I want to lick your pussy," she says brashly, with a small giggle. "But first you've got to have one for me to lick. Put on the bracelet."
The request seems a little unsettling to you. You're not really sure you want to become a girl. Something about the idea of losing your dick makes you cringe a little. But at the same time, you feel guilty about changing Brooke without her consent, so you feel like maybe she's entitled to a little fun at your expense. The last thing you want to do right now is antagonize her. If it will make her happy... you put on the bracelet, and you try to envision yourself as female.
As you think about being female, you feel your own chest beginning to get heavier. You look down, and find a pair of breasts growing there. Your nipples have enlarged too. "Is this okay?" you ask.
"You're not even a C cup yet, baby," says Brooke. "Bigger. As big as you made mine. Don't worry, I'm not asking for you to grow a second pair. I just want you to get a small taste of how this feels."
"Alright," you say. You concentrate on your breasts some more, until they have expanded to DDD cups as well. Next you imagine yourself with a vagina, and as you do, you feel your penis shrinking down, dwindling in size until it's nothing but a tiny nub of a clitoris. You can feel your testicles move back up into your body, gradually becoming ovaries. Your scrotum opens up, and reconfigures into a vulva. Unconsciously, more subtle changes to your body take hold: your facial hair vanishes, your arms and legs slim down, your fingernails and hair grow out a bit longer, your waist takes on more of an hourglass shape. When you look down at your body again... you can't believe your eyes. You've transformed into a female version of yourself.
"Well, what do you think?" you ask. Even your voice is different now-- much more soft and feminine.
"Aww, you're so cute as a girl!" exclaims Brooke. "You should go check yourself out in the mirror. THEN we can start having fun."
Your heart flutters when Brooke says that. It's undeniable-- as worried as you were about changing yourself like this, you ARE a little turned on by the whole thing... especially the prospect of Brooke eating you out. As per her suggestion, you go into the bathroom to get a good look at yourself, and you're absolutely stunned by what you see. As a female, you ARE extremely attractive. Your butt, your boobs, your pussy-- your own body is adding to your arousal. You can't believe it's really you in the mirror; in fact, you feel a slight twinge of reflexive guilt, because to you it feels much more like you're looking at some other random girl who just happens to resemble you, and it's been a long time since you've been face to face with and aroused by a naked girl who WASN'T Brooke.
When you return to the bedroom, Brooke instructs you to sit on the bed and spread your legs. Obediently, you do, and she kneels down and begins to caress your new clitoris with her warm, soft tongue. A feminine moan escapes you as you refelxively lean back. The feeling is absolute bliss. While you run your own hands over your sensitive new breasts, you feel the tip of her tongue slide down your pussy lips and momentarily penetrate you. "Ohhhh... Oh, Brooke, baby... that's... WONDERFUL... Please, keep going. I... I need you to... do more to me..."
"Oh, if that's what you want, baby," Brooke chimes in a tone of perverse delight, "I'm more than happy to oblige. Brace yourself, hon..."