Sharing memory maker?

[KristiKat]

I'm very confused, please help me understand. My family is traveling to Disney with my sister's family. We have MDE accounts and are linkied as Friends and Family. I purchased MM today and linked it to my account and I see where next to her name it says she can view and purchase photo pass photos. Is MM linked to my families arm band? Is it linked to her families arm bands? Do we both have to get photopass cards and link them to MM or does just my sister need to get a photopass card and I link hers to the MM. They really don't give enough information in the FAQ on the Disney website.