Passwords Autopopulating on someone else's devices

Hello, I've searched many threads for an answer to this question, but none of the solutions seem to be working.

Basically, my girlfriend is able to see all of my saved passwords across all of her devices. We've gone through each of our devices and made sure that our personal iCloud accounts do not have each other's devices. I've also toggled on/off Key Chain sharing on my devices and it didn't seem to fix the issue. I would of course like to keep this on so that I can share passwords across my own devices.

I've also notice that when she is browsing the internet, and say she saves saves something to a shopping cart on a store's website, I will get an email reading "Don't forget you have an item in your cart", or similar.

In reading the other threads, my guess on how this occurred is that she signed into her iCloud on my Macbook Pro a couple of months ago in order track one of her devices.

The only way I've been successful in removing the passwords are manually deleting them from her devices. However, I want to make sure this doesn't happen again in the future as I add more passwords and/or devices.

Any tips on how to completely remove our iCloud connections- specifically Keychain Passwords- from each other's devices?