My mum set up an iCloud account and forgot the password, and this caused me to create a new account. The new account works for the App Store and all that, but I can't change the initial iCloud account without the password. Help?

My mum set up an iCloud account for my iPhone 4 but forgot the password. This caused me to create a new account, and it can be used for the App Store and iTunes and all that, but I can't change the initial iCloud account (the one my mum made). My device keeps prompting me for the password every few minutes after updating to iOS 8, and I've tried every option possible to retrieve the password, but I don't even know the answers to the security questions and I can't find the password reset email anywhere and I don't know the back up emails my mum used. I literally cannot find any legitimate way to sign out of the initial iCloud account without entering a password (which neither I nor my parents know). Is there a way for me to retreive the password or change to my new account without the password?