My partner doesn't play many games. She has enjoyed the usual recommendations for co-op games (overcooked, it takes two, stardew Valley etc) but some of the most fun we have had together playing games is playing games that aren't co-op, cooperatively.
For example, one of the first games that sparked this idea was Papers Please. I was playing it and she wanted to watch but we ended up playing for a while and spotting things together. She got hooked so we kept playing until we finished the story. RDR2 was another, but was much more about the environment and ambiance of the game. It was fun to just roam around, stumble upon something and discover it together.
Anything come to mind that could be fun as a shared experience while one person is playing and another is watching?
Edit: should also add she LOVES playing escape room simulator. We've played so many rooms.