46 pounds to lose by Christmas

Well, possible and advantageous are 2 different things, and unfortunately your goal doesn't really fall into either category.

You are talking about averaging over 2 lbs a week. 2 lbs/week is really only for people who are quite obese- I can't find the chart, but generally with 75+ lbs to lose. It requires a daily calorie deficit of 1000, and at 5"2", your maintenance calories likely don't allow for that in a healthy way. Plus, as you lose and get smaller, your rate of loss will slow.

Rather than crash dieting to achieve a certain number by an arbitrary date, maybe try to aim to make some small, sustainable changes that will allow you not only to lose weight now, but continue to manage your weight in the future. Have you filled out your MFP profile? Choose a 1 lb/week goal (definitely no more than 1.5 for a short time), try to log as accurately as possible, and you will definitely weigh less come December.