Help Needed To Undo User Account Changes

I was messing around with the user profiles on my iMac, changing names and pics etc but I accidently lost my g/f's account along with all her folders, etc etc. I didn't delete the account (I think I changed location addresses etc in the settings, I'm not sure) but it froze halfway through and I had to hold down the power button to turn the iMac off. When it came back on her account was no longer there.

As I'm not sure what I did, I don't know how to undo my mistake. What can I do?