Personally I would take another look at the essay. I have written several for other schools and am starting on Duke now. Of all my essays, I have not really needed more then 700 words to articulate my point of view. I would say focus less on the word count and more on the content.
Re-read the essay and see if there are specific lines/paragraphs that really add no value to the overall story you are telling. I would say after this your essay you drop at least 100 words. Do that a couple of times, and when you are not tweaking your essay more then a few words here are there you are now fighting with perfection.
Another helpful tip is have someone read it. If your buddy or someone who knows you but not well is lost in a paragraph here or there you will have a place to focus on. At the end of the day, key is to get the point across you want to emphasize, so if that takes 1200 words falling under their restrictions use all the words.