There is a waiver that needs signed. I know you can pick someone elses packet up if you have a letter from them and their waiver signed but I dont know about registering her. You could always register her online so she gets her packet and waiver in the mail ahead of time and then register yourself there. Just curious, why not register both of you ahead of time and then you can pick up both packets?
Disclaimer: This was the case when I did the half in 2006 and 2008. You may want to contact Disney to confirm. The number to call is (or was last year) 407-896-1160.