I'sd sub the Crunches for Planks, I think it would work out better if you're in the habit of just doing one direct Abs exercise in a routine.
As for the muscle, it wouldn't come quickly, but 1lb of extra muscle helps burn an additional 45-50 calories, so don't be afraid of female strength, becasue it can look very feminine and beautiful as well, despite what some think and by the look of you, you have good genetics, so you will look beautiful and feminine however your body looks.
A stated, keep calories the same and perhaps think of recording them. Females need around 1,800 a day, if they're sedentary and for men it's the good old 2,000, so if you had another 300-400 a day on top of that 1,800, I think you'll be fine, because you'll have extra calories to burn when you train, so you could reduce the risk of burning muscle.
GOOD LUCK and I also say that in relation to your studies. I'm sure you'll one day make a good music teacher