Changing duplicate Apple ID's on iPhones

I have searched the community for answers to this question but there really haven't been any recent responses. I talked to Apple Support about this but just wanted to confirm I'm not going to screw anything up.

I have two iPhones (they have been upgraded every two years) and even though they both have different numbers my apple id is on both of them. I did this because prior to Family Sharing being introduced in about 2016 I wanted to be able to purchase an app and then access on my other iPhone. I know that this can now be done through family sharing.

The problem I am having is that incoming calls to my iPhone are also displayed under recents on my wife's iPhone (this is well discussed in the support forum). Not a big deal but shouldn't happen. I did go into phone settings and turn off Calls on Other Devices after talking to Apple Support; however, they continue to show up when at home and connected to WiFi.

So if I change the apple id on my wife's phone to her own apple id and then invite her to join my family sharing, once I set it up, will she loose any data on her phone (ie. contacts, notes, etc). I do not use iCloud for anything other than Find My iPhone. I understand that an app that she did not purchase may disappear but once she joins my Family Sharing she will be able to get the app back on her phone.

Sorry for the lengthy dissertation but I don't want to mess up her phone.