Renaming Mail Account

I bought a new MacBook Air a month ago and gave my wife my old white MacBook, I wiped it clean (did everything short of reinstalling Mountain Lion) and it's all switched over to her name, except on the Mail program. For some reason, no matter what I do (and I've done everything I could think of with Google's help) her iCloud address still has my name on outgoing messages. I've tried editing it on the Mail Preferences, but I can't even access that info as the box is ghosted, I've tried editing the Contacts card but it's already selected as "[her] car" and I've tried editing the iCloud preferences. I managed to change it to her name on the iCloud preferences but that's still not reflected in the Mail preferences.

Does anybody have any solutions to this problem? Any help would be appreciated, thanks.

Delete the iCloud account in Mail, as well as in the iCloud control panel.