I think wat happened is her dream was like that at the start but due to stamina she knocked out seeming tired and weak and denies the truth that mailing is yet to stop licking her
It's not *un*sanitary, but you should definitely wash your hands afterwards if you want to keep making food(well, ideally you'd put alcohol on then a bandaid, but I'm assuming they don't have either nearby).
Another possibility is that Sakuya started attacking Meiling in her sleep and she incorporated the sensation into her dream as Sakuya going at her while she's awake. Which would make it interesting to see Meiling's reaction when she realized Sakuya was there the whole time.