If you're thinking of recovery, the most important thing is to not do anything to the disk. Don't try to install anything, even the operating system. If all she did is format it, the recovery process is pretty simple. You can use software such as OnTrack EasyRecovery DataRecovery ($200) to restore the formatted partition(s) on the hard drive. If she used some kind of wiping software which repeatedly overwrites the disk, you definitely need professional help. [I'm afraid I don't know of any shops personally who do it.]
In any case, if you have to lay down any money, I'll second the_reject; get the money from her.