I meant to answer Vikki yesterday, but Daniel beat me to it, as so often happens. Thanks, Daniel. :-)
Vikki, I'd recommend Daniel's approach. The other possibility would be to create a new account under your friend's name with her e-mail address. If you have access to her e-mail account you can set up a password and act as if you are her. The advantage of this is that all the history would be in her name. It would be as if she made all the additions and changes instead of you, which might be what you intend. But for obvious reasons that's not generally recommended. And like I said, you'd need access to her e-mail account.