I am trying to remove my sister's name from my car which currently has my name and her's on the title. I can't seem to find information on this at the dmv website apart from Notice of Transfer and Release of liability. Do I do need to change ownership? Or is there a specific form to fill out in order to remove my sister's name from the title of the car.
You can follow these instructions at the California DMV page and transfer the title. Depending on whether you and your sister are titled with AND/OR, you may need her signature to transfer ownership to yourself only. There is a $15 fee and the car needs to be able to pass emissions, etc. This is the exact same process as you would go through to sell the car elsewhere.
I've done this twice in my life. Once when removing my mom from a my first car once I had finished paying the loan (she co-signed for me) and once when assuming ownership of my grandpa's car after he passed.
The transaction is no different than a plain vanilla sale in the eyes of the CA DMV. In your case both owners would fill out the current pink slip and release of liability. You then fill out the transfer of ownership, transferring ownership to yourself. You and your sister are both the sellers, and you alone are the buyer.