D is a strong writer but needs 2 days of stewing and drafts to do a good essay. How much would a poor showing on the SAT hurt her? The rest of her application will be good but not amazing enough to wipe out a significant black mark.
My D is the same – exceptional writer but has to think for quite a while before she writes. I was very pleased when she finally decided to skip the essay part of the SAT.
After her acceptances came in, and after much thought, she choose to go to the one university that she applied to that won’t even look at SAT scores. 
DadTwoGirls - are we talking twins?
I’ve got them and it’s so much fun trying to research 2 sets of schools at once! If a bad SAT essay knocks you out of Amherst’s box that would be a shame, but a bit of a blessing as it’s one less thing to worry about!
Only recommended, not required. I think they’ll be more interested in the CA and supplemental essays.
Top colleges really don’t place much stock in the SAT or ACT essays. The scoring on those things is terrible.
The common data set says Highly [in bold] Recommended.
With study/practice any student who has command of the language can learn to write a top-scoring SAT essay. Simply put, this is not normal ‘writing’. It’s writing in a way to score well on one specific test. In the older format, when the essay wasn’t optional, Son #1 raised his writing score from a 650 to an 800 solely by mastering two study books, one of which dealt with the essay. Son #2 (the one at Amherst) also got a perfect score, working with the same books. The author of that book has a new edition for the new essay/test:
https://www.amazon.com/How-Write-Killer-Essay-Award-Winning/dp/0578169312/ref=la_B005FD3HHU_1_1?s=books&ie=UTF8&qid=1493242801&sr=1-1
Right off the bat the book tells you that for the test you’re not writing as you normally would. You’re writing to score high on the essay. It has the student ready to write within a minute or two of reading the prompt. Not much thinking is necessary.
I appreciate that this may not work for everybody, but it was very very helpful to my kids.
Echoing Asleep, and it applies to all of the test’s components - it is a matter of playing the game to master a specific skill. My D took the SATs 3 times - each time focusing most on one of the tests. Since Amherst (and most schools) super score, she was able to raise her two lower scores by 200 points and all the prior ugly scores had no impact. Your D needs to be motivated - and then practice, practice… . We chose weekly lessons with a tutor - certainly an expense not everyone can afford, but the investment is paying huge dividends now.
Is this purely about the essay and not the Writing score? If so, I really would not worry about it. I don’t think much stock is placed on the essay score anymore. Maybe Princeton still does, but research the schools your D is interested in to see if they even look at/require the essay. I’m seeing more and more schools that don’t.
@suzy100 - This is in the Amherst forum because they want it. I’m checking out the schools on D’s definite/likely list for those that don’t superscore or do require the essay.
I got in with a 24 on the ACT essay component, so I definitely wouldn’t worry too much about the essay score! Although my composite was a 35 and I got high scores in English and Reading so I’m sure that helped me and balanced out the essay score…
@rmsdad - what materials did your D use? Our plan is to focus on Math for the June test (33 days!), Verbal for August, and then see if we’re done or need one more pass whenever the next one is. Deciding on SAT only has helped them focus and one section at a time is even better though it invites boredom.
@byadg123 - We used the The Official SAT Study Guide and The Official SAT Online Course.both by the College Board;. We are getting ready this summer to start the study process with D2. We will also be using the book from the College Board (the updated version) and will make as much use of Khan Academy as we can. This time around, it looks like I will have to be the tutor as the prior one retired and there is not another in our small town. Not my idea of an ideal summer, but it is one way to spend more time with D2.