My ex-girlfriend uses my Apple ID to log in to her iPad. Do I have to give her my Apple ID password to reset it? She asked me to give her my Apple ID password to log out. But I don't want to share my password. She said she need that password to log out the iPad.

Do I have to give her my password?  What else can she do?
Don’t just give the password - that gives full access to your account - she could change the password on you... Make it that you enter the password and reset... Either meet or she sends you the iPad...