Does так push the meaning closer to 'My older sister is SUCH a good cook' rather than simply stating that she is a good cook?
Yes, it does.
Funnily enough I worded my answer exactly like that and got marked wrong!
Actually, I think this can only mean that she cooks well, not that she is a good cook. I think так goes with verbs, like "to cook" and такая/такой/такое go with nouns, like "a cook".
I had forgotten this. Thank you.
Why not an English translation for the answer?
When you click the textballoon icon (like you did to post your comment) you see the translation at the top of the screen
I wish they'd tell you what the sentence meant after selecting your answer whether right or wrong.
In this comments section, the translation is given. Look at the top of the page
It's more natural to say somebody is a good cook rather than saying that they cook so well.
I agree. In fact, its borderline bad English. Almost no one says it in this context.
That's why I prefer to learn languages in the comments section.
My older sister cooks so good....why is not ok?
Because "good" is an adjective and adjectives modify nouns only. The verb "cook" is the word being described and adverbs describes verbs. "Well" is the adverb form of "good".
"My older sister cooks really well" should also be acceptable.