Is it possible to reset apple id password without old passcode?

My aunt had died one year ago. She left her phone (it has no passcode), and we've decided to keep it. My sister owns it now. We're trying to get her photos from her iCloud and sign out her account from the device. However, we cannot remove her Apple ID since it requires a password, and when we try to reset the password, it needs the old passcode (which we do not know). Is it possible to gain access to her account? We have her email, phone number, and, of course, her phone. We can also provide information.