You're welcome. Undoing the merged contacts will require you to go through and delete the ones that you don't want on each phone (assuming you don't have a clean unmerged list to re-import to the phone). First decide who will keep the existing iCloud account and who will change to a new one. Then, on the phone that is changing, go to Settings>iCloud and turn off syncing for each of the services listed (contacts, etc.). When prompted, choose to keep the data on the phone. Then scroll to the bottom and tap Delete Account. (This will only delete the account on this phone.) Now set up a new iCloud account on this phone with a different Apple ID and turn on syncing again for contacts, etc. Next go to iCloud.com on your computer, sign into the new account, go to contacts and go through and delete the unwanted contacts. (You'll also have to sign into the other iCloud account and delete the contacts you don't want on the other phone as well.) That should fix the contacts on both phones.
As for the music, connect her phone to iTunes, go to the Summary tab and check "Sync only checked songs and videos" (if it isn't already checked). Then in the music library, uncheck each of the songs that she doesn't want on her phone. When finished, sync her phone and the unwanted songs will be removed. You may also want to take a look at this article on ways to sync multiple iPhones on one computer.