Will switching Apple ID's on my phone make me loose all my content?

When my wife and I first got iPhones back when they first came out, I created a single iCloud account for myself and we signed in to that account with both our phones (this was before all the family sharing was even a thing back then). This worked fine as all our contacts, pictures, etc was shared/synced between our devices and we liked that at the time. There was also the option to receive each others iMessages, but we had this turned off in each of our phones messages settings (Settings -> Messages -> Send & Receive then unchecking the other persons phone number so we wouldn't receive them).

Unfortunately we have now since separated and she needs to get her own iCloud account, but she is worried that signing into a new account will cause her to loose all her current contacts, pictures, notes and everything else that was syncing to the cloud. When she goes into Settings for each item that would sync to the cloud and turns off the sync, there is a message stating that all data on her phone (for that item) will be deleted, which is frightful so its left on for now while she is still signed into my account.

My question is, what would happen if she were to simply log out of my iCloud account from her phone and create/login to her own iCloud account? Would she loose any contacts, photos, apps or anything else?

All Apps currently installed were downloaded from my account, and although most were free, there may be one or two purchased apps (but not subscription apps) present on her phone.

Would she loose access to any of these apps she currently has installed since they were downloaded from a different account than she would be signed into?

I also have the understanding that older photos on the phones will only keep a thumbnail version locally on the phone and the full picture would be on the cloud. When you then actually need to view it, it will pull the full version from the cloud back to the phone (or something similar). If she switches accounts, I assume she would no longer be able to pull these full versions back to her phone. How would this situation work out?

Any advice on how she can switch icloud accounts on her devices without loosing any current data would be appreciated.

Thanks