Do this: Go under start > Run > MSconfig > (tab) Startup > *Find the program's ID and uncheck it.* It should then stop booting with Windows. You do realize, however that she will most likely notice the keylogger has been deactivated and you may suffer worse consequences.
It is also a possibility to boot under Safe Mode and remove the entire application as a Power-User, assuming it will not require a password for that, either.
Personally, I'd go with what has already been suggested. A windows-live boot CD, or a Linux-live boot CD. These will enable you to run a copy of Windows from the CD drive. The major downside is that, because it is a CD, you will not be able to permanently install programs, and the availability of program installation will be based on the amount of RAM your computer possesses.