It's a matter of opinion, in a way.
Generally, when it comes to anything online, using your first and last name (especially if you are young) is not always the wisest thing, unless you trust that your information is secured on a trusted site.
While FeralHeart and its staff will not be a problem, there's nothing to say there aren't others who play the game who might try to search for your friend elsewhere online by means of seeing their name.
Others have made their real-life names their usernames, and while they have been alright, I still recommend going by a different name, just for the sake of security. If she wants someone she meets online to know her name, then she can do so as she pleases-- but it's not the best to run around on the internet showing off your name, usually.
I recommend making a new account.