Google Photos is automatically sharing my pictures to my wife without asking permission?

My wife and I are both on the iPhone 12 running iOS 14.2. We are both on Google Photos iOS version 5.19.341316636.

When I take a picture using my phone, it automatically shows up on the “Photos” tab inside Google Photos. No problem there – I have given Google Photos access to my camera roll.

But the strange thing is that those same photos are showing up in my wife’s Google Photos app on her “Photos” tab. These photos don’t appear anywhere inside her iOS photos or camera roll. She is logged in to her Google account on her device, and I am logged into my account on my device. I have backup turned off in Google Photos, and neither of us have ever activated “Partner sharing”.

How is Google sharing these photos automatically, and how do I make it stop?