Problem with 2 iPads in one house.

So here is the problem. We have an iPad 2 and an iPad 4. The iPad 2 is my wife's and uses our primary apple I/d as its also her email, @virginmedia.com. My daughters ipad syncs to the same account but has her own email address gmail.com. Yesterday I noticed all my iPhone contacts have appeared on both devices despite the iCloud not set up to share contacts. So I got rid of that and now whenever my wife sends an email it says she is from my daughters account. I should point out the both email accounts are on my wife's iPad so we can monitor her emails. But she has it set up as the primary email being gmail.
I should also point out that we have had both of these devices a while and I haven't recently synced them with my iMac (which is what we back up to). Why has this just started happening?