Say a modern chemist or engineer is landed in a different world with early 1400s Medieval level technology and social problems. She (yes a woman), is immediately considered a witch for many obvious reasons. However this world does not think magic evil, unlike the middle ages on earth, and instead revers it as part of its religion (even though real magic DOES NOT exist, just science). A Lord or King immediately takes her and basically offers her protection in return for her 'magic' and basically marrying him and having his kids. She agrees because she doesn't want to die from the various diseases/poverty/famine that befall the peasants and she's clueless to how this world works. (Also language is not a problem as she was taken in by a kindly priestess organization that taught her in exchange for the things she had with her when she landed in the world, such as her 'fine' clothing and jewelry ect...)
So, would these ideas be realistically implementable with medieval technology and resources, and would a modern chemist/engineer have the knowledge needed?
Umbrella (invented by China already but this is a fantasy Europe that has no contact with any fantasy Asia)
Better mirrors through use of the silvered-glass method (I doubt this one because of its chemical dependence, but maybe?)
Agricultural revolution :four field planting method (which was not pioneered I don't think until 1500s and not popularized until 1600s) using turnips and clovers so no field is left fallow, thereby greatly increasing food production and allowing for livestock to survive winter months where they might not have had enough food to support them - their food being the turnips. And perhaps introduction and creation of the chinese three-shared plow, the lou-li (plow-and-sow) implement, and the harrow (which werent introduced to europe until the 1600s I think?)
Discovery of peat and introduction as use in fertilizers?
Early introduction of the Ice Trade through use of ice houses and showing nobility how to create 'ice creame.'
Method for canning and storing food by putting it in glass jars, corking and sealing it with wax, and then boiling it. Also maybe pasteurized milk. (Neither of which were discovered until the 1800s and lasts longer than medieval methods with honey or lard)
Spinning Jenny/Water frame/flying shuttle. (Would these even be viable or are they just for cotton and not wool?)
Introduction of modern metric system