You can change the admin password via a command line without having to enter her current password.
Simply go to the computer whos password you need to change, run cmd as Administrator (Right click > Run as Administrator)
Then type "net user" this will list the users currently installed on that computer.
type "net user administrator * "(or replace with any other account name)
you will be asked to then enter the password you wish to use. Note that when you type the desired password in, you will not see any text or indication that the password is being typed in.
Just hit enter after you have typed it in, and you will then be asked to type it in again to confirm.
Then when prompted on your computer for the admin password in pstools, you can just enter the one you set it to a minute ago.
Appologies if this is not actually what you're after, I'm only on my first coffee this morning