How to erase my ex-girlfriend´s user account

I quit my girlfriend and she doesnt want to give me her password in order to erase her user account from my beloved black macbook. Could any body give a hint on how to disable it or erase it witout the password?.
If there´s a way please tell me i dont want to see her account when i use my laptop. Thanks in advance and congratulations for the forum since i am new on it best regards to all users

Assuming you do have admin privileges on your user...

Go to System Preferences > Accounts
Click the lock at the bottom, authenticate with your user id/password
Highlight her account id, then click the - sign down below.

Erasing account user on my MacBook !!

I recently quit my girl and she had her own user account in my beloved black MacBook. now she wont tell me her password which i think is necessary to delete or erase her account ( which i just cant stand seeing when i use my MB). Can any body please give me any hints on how to do it? .
I will never be thankfull enough Hail all Mac users!!!

NOTE: Merged crossposts