Is this the BIOS password or the Windows login password?
If it is the BIOS password, then you need to contact Acer. However, you need to be the original owner / it must be registered under your name.
If it is the Windows login password, then... you are likely to be screwed, especially if she just typed in a string of random letters. Sorry, but that means you need to reinstall Windows to gain access to your laptop again. That means anything on the C: drive will be deleted.
If you recreated a separate Administrator account and you know the password you can access your laptop that way...