If you don't have a password recovery disk, I think you can perform a clean reinstall of the software. That is, if there isn't anything you need on the computer.
Any chance she made a password recovery disk but forgot about it? I think Windows walks you through that process when you first boot it up. If you have all of the original software, it could be with that. It has been over a decade since I used a PC for my own use, and the new windows isn't anything like the old windows.
I bet if you call the Geek Squad like Don suggested and tell them what happened, they will tell you if you need to do a clean install or if they can do something else if you need what is on the computer.