So, if you go into control panel and click User Accounts you get the message? If you can get in there, click Change User Account, click her account, and you should have an option for Do Not require password or remove password. By default, when you create an account it is an administrator so if she locked you out, she just punked you.
There are ways to recover a password, but they work better in domain environments. I have not used this on a home computer and do not know what the oucome would be. Either way, that tool lets you reset the account password. It does not tell you what it is.