There's the unfortunate possibility that yer friend will need to register for a new account. If a user is made but is not activated right then before the registrations close again, that user will over time become restricted/cut off (both in-game and on the forum); thus the results bein' what yer friend currently faces.
Although I advise contactin' a staff member about this: >>Click here!<< (http://feral-heart.com/index.php?option=com_content&view=article&id=28&Itemid=52)
Since yer friend cannot remember the e-mail she used with said account, perhaps tell whichever staff member ye' contact yer friend's user. They can take a gander at the user database and tell ye' (in which ye' can pass on to yer friend) the e-mail information and other little tidbits in hopes of yer friend retrievin' her account once again. I wish ye' both luck.
SilverLark I advise you look at what Vespian said and that might help.
Honestly all I can do is say the same thing as Vespian and Chesire did.
Ask a staff member to check the datebase for your friends email (using their username to find it) and passing on the information from the datebase to you/your friend.
I hope you find out what the problem was/is soon.