
Well... if this were a real story, our MC, without realizing, making sweet potato popular with nobles in order to sell more tea she will take away a good food for the commoners!
In other words, more popular is the sweet potato more expensive it will and many nobles will try to make it exclusive for nobles.
So, it will be harder and harder for commoners be able to eat a food they always ate that was not expensive and was filling.
So, she most probably will cause some people cannot feed their family with sweet potato like they used to do it!!!
This is really egoist from the MC!

I'm not an expert or anything so I'm not really sure but what she is doing is introducing sweet potato to nobilities that doesn't want "commoners food" if the nobilities accepts the food yes it will help farmers but then they will increase the price for the good quality ones to accommodate the nobilities "rich taste" and the left over bad ones will the ones left for the poorest of the poor(beggars) when in fact they can buy those things before for cheeper prices (not really sure about this but this is just my thot.) I know her intention is not bad or anything

Not necessarily.
The nobles control the land and its production so if sweet potato increase popularity Increase in demand More land allocated for production Increase in produce Lower market price.
Also is easy to cultivate. It can withstand harsh weathers compared to other vegetables and can be stored for long Easy production and Long storage life Cheaper production and trading costs Inexpensive, sufficient supply, long storage life = a good common food source.
is an imported good (As mentioned in the story) Local produce is cheaper.
Other nobles cultivate the for its so the (I assumed) would be sold.
There are also negative results but it all comes down to the royalties to control price increase and trade manipulation.
Honestly, he is really hot!!!
True things have to be said.
(づ ̄ ³ ̄)づ