You go back to her with your old legs under one arm and your magical sword in your hand on the other side, not really sure why do dit take your sword. Once in front of the woman you suddenly hit her with the pommels of your trusty sword. You don't know what came over you, but you notice 2 things.
First, as soon as the pommels touch her it start to glow white, and so do her eyes, and her body rumple in a heap in front of your door.
Secondly, nobody notice her, it's like you're the only one that can see her.
You hurriedly draw her inside you house and close the door, before looking at your phone and see that no trace of the messages you exchanged are left. That's when you understand: You can use the pommels of your sword to temporarily ‘erase’ someone from reality, so you can take a physical characteristic from someone unwilling to exchange.
Looking at both the legs currently connected at your body and the brunette's torso, you notice she's almost perfect. You just wish her muscles were more toned. (That and the size of her boobs aren't what you would prefer, but they'll have to do for now.)
You decide to see if you can use your sword to open your old legs and take out their muscles without damaging or changing anything else. Since it works, you exchange them with the muscles of your current ones. It works, giving you strong but still feminines and nicely tanned legs. Your old ones look rather spindly now but you don't plan on taking them back ever, so not your problem.
Deciding to experiment a bit more, you use your magical sword to peel of the skin of your unsuspecting victim, before also taking her boobs and the rest of her reproductive system. Since it doesn't seem to have any adverse effect, you also peal the upper part your body.
Ready for the next phase, you places her breasts on your torso, where they attach like they always were part of it. You do the same with her uterus, (fallopian tubes and ovaries include) which you take care to correctly align with your vagina. Your new reproductive system rearrange the rest of your internal organs to get the necessary place for itself, it's a bit uncomfortable, and even painful at times, but still notice no undesirable effect. Then you cut your Adam's apple and place it of the brunette.
You were about to put on the skin you stole from the still unconscious woman, but notice your current hands aren't very feminine, skin or no skin, so you exchange your left hand with hers, then do the same with the right one, before putting on her skin. Somehow, that cause your body to reshape itself. Going to the nearest mirror, you're relieved to see it was to give you the hourglass figure you didn't dare to hope for, but didn't take away any of your muscles. You even have her face and her long, silky hair, but the eyes behind your new eyelids are still your old ones. You find your new self absolutely breathtaking.
On your way back to the former woman, you take the old photo of your kid self fishing with your father with you. For now it still picture a kid with a boy's upper half, but is a girl from the waist down.
You put the photo on the ground and make your victim wear your old skin, which immediately become their own, before you give them your previous legs. The former brunette is now entirely a scrawny version of your old self, which you find rather disgusting.
Looking back at the photo from your childhood, the half-boy from earlier is now entirely replaced by a very tomboyish girl who is just as overjoyed at the fish she captured, your father not far behind, clearly proud of you.
Before waking up your victim, you decide to inspect the house, and rapidly discover your entire wardrobe was changed to accommodate your new body (and grew a lot), and that your bathroom is now overflowing with make-up and skin-care and hair-care products. (And somehow, you now remember when and how to use each of them.) Your shampoo and body wash also got replaced by different ones.
But that's the only thing you find changed. Your movie collection didn't become a pile of chic-flicks, your video-games and old action-figures are still present. Even your porno mags stayed unchanged, even if the splotch of sperm that used be on some pages are replaced by another substance. Stowed near your pornos, you find a box containing an extensive collection of dildos and vibrators. The new you is quite the naughty girl!
Reassured that only the strict necessary had changed, you go back to the main room and try to wake-up your victim, but he stay unconscious, with his eyes glowing. You decide to place their body near the sofa, tap their temple with the pommel of your sword and hide the magical weapon under the aforementioned sofa as fast as you can.