Trying to play Campaign Co-Op with GF

[Tuesday]

Gonna try to make the situation concise with bullet points to be concise. I don't mean to be rude.

1. I am trying to play WaW Campaign Co-Op with my girlfriend.
2. We have both purchased the game on Steam.
3. I bought my game before the keys ran out. We bought her copy recently.
4. We both have our games and PW launchers up to date.
5. We both have PW accounts (and follow eachother).
6. We only made her account recently.
7. She is unable to host LAN via the game's native menu.
8. When I host LAN, she has connectivity issues, so I am attempting to run it with her hosting.
9. We live in the same house and are connecting to the same router.
10. We are unable to play with native LAN (instead of PW) because of the whole Online Account thing. I don't get it, either.
11. I have attempted to host an online match on her computer. It results in "Your authentication ticket could not be verified because the server you are trying to connect to is not authenticated to Plutonium."
12. I have attempted to start a solo match with "sp_minplayers 0" on her end. Same prompt.
13. I typically attempt to connect with local IP address instead of public IP address.
14. Connecting with public IP address creates "Failed to log on." on the cmd.

What do you guys suggest?

Thank you.