Shared Info through Apple ID

Hi, I logged into my Apple ID (through settings) on a friends iphone to gain access to find my iPhone and then logged back out. I now have a new phone and have set up my Apple ID on this device. However, my friends Apple ID/ iCloud is somehow linked to mine as I can see both our camera rolls and also some apps that I download are logged into their account already (like Spotify). How do I unlink these accounts and clear their photos from my camera roll as well as clear my photos from theirs. Thanks for any help.