This is too wack

Can I ask which part of the manhwa is wrong? It’s true that scurvy is caused by lack of vitamin C and rosehip tea can indeed provide a large amount of vitamin C

The issue is she is a woman in a place and time where women didn't handle business and were expected to the their happiness with their husband's (which we have seen in the chapters already.) Chloe suddenly has a one-eighty and her husband starts to like her because "Oh, she has a personality and interest in something that makes her look absolutely beautiful."
The no research to back her up comes from no one else realizing the cause of scurvy. And they don't even know what vitamin C is. She's speaking gibberish to them. She's a woman with no medical background and a seemingly "lucky break" with business. Using the grandma as proof of her thesis will go far enough for them to try on maybe one ship (since it won't kill anyone at least.) Ugu is right in that they would normally treat a headstrong, confident, and knowledgeable woman as a witch. We know what she is saying makes perfect sense but the time she is in doesn't match that. In fact, far fewer people would take her seriously. Gospel from the mouth of her husband but heresy from her own.

Yes, this is literally all I wanted to say. Thank you.

I’ve seen various isekai that try to explain more modern concepts and knowledge such as dr. Elise however, in those specific mangas/manhwa we can see the main characters actually creating a basis for their knowledge. They could cite previous scientists in their world that had similar studies and findings in which they expound their modern knowledge. Since they had those backing, the people in their world would more likely believe the reincarnated characters.

In this case, she literally has no set up for what she knows. Even her knowledge about tea is suspect because for some reason the same kinds of tea exist in her world? The location of the teas and the various cultural meanings they have are also for some reason similar to the ones we have in our world, which just doesnt make sense.

She also continues preaching about modern values without actually explaining it. Like the incident with the tea house. She wanted the place clean and hygienic. She told the man what to do without even delving into the why (which is the most important to solidify their actions.)

She introduced terms unfamiliar in their world, like vitamins. If someone wouldve heard about that, they would assume she was speaking some random magical word, and would rightfully doubt what she’s saying.

Ive been loving this manhwa and honestly, no hate, but the suspension of belief is too high.

On the hygiene one, she could have easily explained why without any scientific backing. She could have opened up with how they spend their morning or when they go home at night. Do the employees own a dog? Imagine licking it, since they probably haven't washed their hands since petting it. Do they have children in their life? You know how many kids pick up poop? And it doesn't have to be the child they interact with either, as they are all germ factories spreading amongst each other. Imagine all the snot on their sleeve in a cup you are about to serve.
Or even better: take slices of bread each cut from a different knife that had previously cut meat, fish, etc and leave them in the window. That mold would be enough too. You are right she didn't explain anything and made demands; that kitchen will fall into bad habits when the boss is lax. I know she wasn't in the health field when she was alive but we all grew mold at some point in our childhood years (some unintentionally.) She knows exactly why hand washing works, even if germs and viruses would send her to the stake (it can be replaced with far simpler vocabulary.) The fact she knows about scurvy tells us something about what our educational system finds important to teach children.

I am here for the tea p*rn and the side romance. Thinking about these things makes me a bit upset but I won't stop reading.