deleting an account without loosing device contents

I currently own an iphone 5 and an ipad mini

and due to a family disagreement I have had with my sister she has told me to get my own iTunes account as she no longer wants me using hers anymore.

I have created an account and logged into it on my I phone and my ipad and now I have updates to do its asking me for her user password for her account even tho I have put my apple id into the devices and logged into iTunes on them and have also logged into icloud it still wants her password.

Does anyone know why this is still happening seeing as she tells me that she has been into iTunes and deleted the devices out of her account.

when I look on both devices in the settings it shows my apple account as being connected to both iTunes for the apps store and I cloud services but still requests her password am at a lose as to what to do without wiping the entire phone contents and starting new