You don't need the new ID, she does. All your content is under that ID, don't give it away.
(1) Your mom will have to get her own Apple ID. No way around it, but it's not all bad if you also set up family sharing afterwards.
(2) First you need to talk her through signing out of the Apple ID she is sharing with you - NOTE let her know in advance that she can choose to leave the data on her phone when she is asked by her iPhone.
(3) Then after she creates a new Apple ID and she is signed in, she should be asked if she would like to merge her data on the phone to the iCloud account that she just created -MAKE SURE she knows to choose that option.
(4) Go to your own iPhone settings and then to your Apple ID settings. (in iOS 11 click on your name at the top of screen)
(5) click on "Set up Family Sharing" and choose Get Started.
(6) Follow any instructions to send her an invitation to join your "family".
(7) After she joins your family sharing (you will have to agree to pay for all apps and media that she buys) she will be able to continue using all the apps and media that she downloaded under your Apple ID.
(8) Make her agree to pay you for any excessive use of buying media.
If she refuses to cooperate and you must force her off your ID, do the following:
(1) Open you iPhone settings and then go into your Apple ID settings (in iOS 11 click on your name at the top of screen).
(2) You will see a list of devices that have signed into your iCloud account (closer to the bottom of the screen, below iCloud and below iTunes & App Store settings)
(3) You should see the device that you want to cut off click on it.
(4) On the next screen you should see a "Remove From Account" button in red letters.
(5) Use that to remove the device.
(6) Then immediately look back at the Apple ID settings near the top of the screen where it says "Password and Security".
(7) Click on "Password and Security" and choose "Change Password".
(8) After you change password she can't sign back into your account.
(9) Fix your password on all of your other devices signed into iCloud.
(10) Let mom know what you did and let her know how to get access to her data and apps by joining your family sharing.
I do not know exactly what happens with the "Find My Iphone Lock" on her phone when she is forced off, but she should be able to unlock the Apple ID with your new password, which is unfortunate as you will have to change your password a second time to keep her out.
[doublepost=1519117339][/doublepost]Okay, you should be able to set up a new Apple ID for just your iCloud data syncing, by signing out and keeping the data on your phone, and then signing into a new iCloud account and merging data.
Then keep using the old ID only for the Apple Store and iTunes Store, and home sharing. YOUR MOM WOULD KEEP USING THE OLD ID FOR EVERYTHING, but you wouldn't. You'd still have to sing out of iCloud on all your devices and then sign into the new one.
I am using two Apple ID on my iPhone, one for iCloud and one for the stores, while my wife only shares the store account and has her own iCloud account. But we set it up that way in 2009 when it was .mac or mobile me or something. I forgot all about that option.
[doublepost=1519117430][/doublepost]PS: I know moms - mine keeps texting my home phone number instead of my iPhone, or calling me at 7AM when she knows I sleep from 2AM to 10AM.
