How to "shift" to Family iCloud?

For years my wife just used my Apple ID for music, apps, purchases, photos, and calendars, etc, etc. It worked fine for years.

But we've recently been getting each other's texts, facetimes, calls, etc. And even though we've made 1000% sure each other's phone #s aren't selected in those apps, we still get crossover.

So all the advice I've gotten said "have your wife get her own Apple ID. So she did! And I sent her an invite via my iPhone's iCloud settings. But her phone is still on MY apple ID.

Honestly, we're a bit scared to SIGN OUT of my apple ID on her devices, and then sign in w/ her new one…

Will that delete anything? Will anything stop working? Will photos stop syncing???

Any help and advice would be much appreciated 🙂