Hello:) Take a look at this info found by searching in this excellent forum. This will happen if you are sharing the same iCloud account and are both syncing contacts with iCloud. When you do this, you contacts are merged and will appear on both phones. First, be sure to NOT delete your contacts from her phone. If you do, they will also be deleted from your phone and you will lose them. To solve this, she needs to have her own iCloud account with a separate ID. (Note: you can continue to share the same ID for iTunes; it does not need to be the same as the ID used for other services such as iCloud.)
To migrate your daughter's phone to her own iCloud account, on her phone go to Settings>iCloud, scroll to the bottom and tap Delete Account. (This will only delete the account from her phone, not from iCloud. Your phone will not be effected by this.) When prompted about what to do with the iCloud data, be sure to select Keep On iPhone. Next, set up a new iCloud account using a different Apple ID (if she doesn't have one, tap Get a Free Apple ID at the bottom). Then turn iCloud data syncing for contacts, etc. back to On, and when prompted about merging with iCloud, choose Merge. This will upload the data to the new account.
~Katana-San~