[iMore Question]

Wife wants to be able to keep her contacts and calendar on her new phone but everything is intermingled together with mine

[Tartarus]

Hi, welcome to iMore.

Ok, here's what you're gonna do.
First make a new Apple ID for your wife, set up the new iPhone using that ID. Restore as a new device if your contacts and calendar is already on it.
Then go to iCloud.com and log in using your own Apple ID, go to Contacts, at the bottom right click ⚙️ settings > Select All, click Settings again and choose to Export vCard. Save it to a location where you can find it easily.

Then log out of iCloud.com and log in with your wife's newly created Apple ID, go to contacts again, Settings and choose import vCards, select the file you previously saved and wait for the process to finish.
Then on her iPhone go to Settings > iCloud and enable at least contacts and calendars. You can choose to enable the rest too, if you like.

You will now see all contacts are starting to appear on her phone.
You can either choose to delete the unwanted contacts on the iPhone itself or on iCloud.com. It works both sides.

Repeat this process on your own iPhone or iCloud account on iCloud.com as well to delete contacts meant for your wife.

In following above steps your wife will need to redownload apps she want to use.

You can either choose to download them with your AppStore credentials or with her own credentials.
My advice is to download paid apps with your own credentials to avoid paying again for them.

As most apps are web based like Facebook, Instagram and twitter your wife will have lost none to few information in her apps.

Also, following above instructions will allow your wife to set up her own FaceTime and iMessage as well.

If you have any further questions, please join our forum. We're happy to help.

[Ledsteplin]

Simply put, you both need your own Apple ID and password for iCloud, iMessage and Facetime. You can share the iTunes ID so you can share the purchases.