windows created a second profile on its own and moved all my data onto it

hello,  i have a question for you. we recently went to a job site where the computer's operator let her hard drive fill to capacity; so much so that the  programs were unable install updates so it started throwing massive numbers of hotfixes into random folders in her c drive which filled up her c drive completely. which then caused the antivirus to be unable to update.  long story short, after we removed her temp hotfix files, freed up room on the hard drive, did a checkdisk to help fix errors, and dealt with the virus that happened because norton couldnt update. then we noticed windows had actually removed all of her data from her normal user account, put it on a second account the computer created on its own. so now i have two user accounts, one being named the old accounts name and a new one on the local drive that has all the acccount info on it. so i was curious as to what happened here and how to fix it; any assistance would be much appreciated.