Transferring ownership of a deceased person's MacBook Air

I would like to be able to change her MacBook over to my name and ID.I spoke with an apple support tech and they said they couldn't help me. There must be some way to change the ID and password on the device of a person who is deceased. If anybody has a solution please help me out.

[Re-Titled by Moderator]

Original Title: my sister just passed away andI was gifted her nearly new MacBook Air have her ID and password, any help would be great.