Does she have access to the machine?
If not check for the obvious legit stuff first, so look in add remove programs and look for anything like logmein, VNC or any other remote access/desktop software (if you don't know google the name and see what it say it is). Also check that the windows remote desktop isn't turned on and reset all passwords on the computer for all user accounts!
a full scan with most antivirus software and also a scan with malwarebytes should pickup any keyloggers that might be installed depending on how clever/good at this she is.
which is another question.... what level of computer user is she?