Two iphone 5s sharing contacts and photos?

Me and my girl purchased two iphone 5s yesterday. When the first iphone came out we purchased two of those and have been using the same apple id since. I hated the iphone 4 so got rid of it and went to android. She continued using the iphone with that same apple id. Now i ditched android to go for the 5s yesterday. So she gave up the iphone 5 for 5s and i gave up my galaxy s4 for 5s.
All was going good until my battery died… So i charged it. And after the phone turned on, all of her contacts and photos are showing up on my phone. After restarting hers, my contacts or phone numbers don't show up on her phone.
what is going on? How to fix this?
at one point i did sign into icloud from her phone with the apple id but then quickly deleted the account because she said she doesn't want to use icloud. Does that have anything to do with it? If yes, what should i do since i already deleted icloud account from her phone.
one more thing, the pictures showing up on my phone are not all stored on her phone, some are from her macbook. Which makes this even more confusing.

Icloud might have something to do with it, but any social networking apps will sync photos and other information onto a device, eg. If you log into facebook on your girlfriends phone then your photos you've posted on your facebook account will sync to her phones photo library.

Your icloud account is your apple ID, so if you both use the same then of course the backups and sync will be the same. I would just sign out of icloud and then each get your own ID separately so that each of you can do your own backups, otherwise you are basically sharing and saying we want the phones to be the same.
As far as the Mac, thats signed in with icloud too, as photo sharing, imessages, etc, will occur across all. She can use her own ID for Mac and her phone, then you have your own ID for your phone.

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