First, when you begin an exercise program or change anything about your current exercise program (duration, intensity, type) your muscles will retain more fluid which can mask fat loss on the scale for up to the first 6 weeks.
Second, you are way undereating. 1200 cals is the *minimum* intake a woman should consume while losing weight to ensure she's meeting her nutrient requirements. If you exercise, you should be eating *more*. Personally, I'm 5'2 115 lbs and would lose weight quickly (1-2 lbs/week which is very fast for someone in their healthy BMI. If you are in your healthy BMI already, you should aim to lose only 1/4-1 lb/week) eating anywhere from 1500-2000 cals (I am pretty active though) but point being, you shouldn't be afraid to eat even if your goal is to lose weight. In fact, undereating can actually work against you and slow weight loss.
Not to mention if you are weight/resistance training you *need to eat* you can't grow muscle by starving it, in fact... you'll just wind up burning away muscle along with fat. This will cause you to maintain or even increase your body fat percentage. If your goal is to get lean and toned. You're going to have to eat and feed those muscles. You are not going to want to be any starvation diets and you're going to want to aim for a slower weight loss. No more than 1 lb/week MAX. 1/2 lb/week perferably. That's -250 to -500 cals/day from your total daily energy expenditure.
