"Invest" in this sense does mean the same thing as "infuse." But it doesn't necessarily mean a weaving together. It means that she is essentially giving idiomatic English the qualities of the Chinese language. In this way, she is simulating the Chinese language using English which is why answer choice (B) is the best answer.
I think you figured out more or less what "invest" meant, but you got too attached to the "integration" end of your definition. The lesson I think you should take away from this question is not to get so attached to your specific prephrase that you allow yourself to choose an answer even though you know part of that answer is wrong. As soon as you realize that the part about achieving a savings in price in answer choice (E) is off, eliminate it. If part of an answer choice is wrong, then the answer choice as a whole is wrong. Remember to take the answer choices as given--don't try to make an answer choice correct, look for reasons why it is incorrect. The majority of reading comprehension questions are Must Be True questions so you should be just as hard on the answer choices as you are with MBTs. In this case, you could have eliminated answer choice (E) and then looked at the other answer choices to see which of them was better at describing Kingston's use of the English language. Don't be afraid to adjust your prephrase a bit when you don't get an answer choice that matches it exactly and never choose and answer when you know part of it is incorrect.
Hope this helps!