As for the second line, it could mean, that Sakuya usually comes to bathe with people, but there were no instances of her doing it in the story so far (AFAIK), so I thought the line would be more consistent with the scene as it is now.

It's more like she was thinking how much of a blockhead Meiling was, as you phrased it, and didn't pay attention to why she got herself in the tub while Patchouli didn't pay her doing any mind, continuing with her book until Sakuya blurted out her comment about Meiling and realized something was off. Well, I edited the notes fitting that. If it's wrong, editing it again is just fine but let me know about it okay?