Thank you for your posting.
I would not re-take your GMAT. I would use all of your available time and energy to make sure your application is as strong as it can be. A 3.2 GPA (while not awful, is not great) and this is your entire margin of error in your application. Thus, all aspects of your application have to be compelling and competitive. No room for error. An additional 30 points on your GMAT is not going to make a difference in your candidacy.
As for the schools you have targeted -- MIT and Columbia are very numbers driven and your GPA places you at a distinct disadvantage. I would recommend that you replace (or add) Wharton to your list -- as Wharton is very women friendly. Stern is the easiest of all the schools on your list but you have to really sell admissions that it is your top choice.
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