Females do not have enough testosterone in their bodies to gain a great deal of muscle. So put your mind to rest on that. Many females have the mentality that they should restrict their calorie intake too much which is counterproductive to weight loss. If you are taking in between 1200 and 1500 calories daily and burning 600 to 1000 calories in cardio you put your body in too much of a deficit. Your body requires calories for its normal functions, then you put the stress of cardio on it, which burns more calories, which is great, but you need to make sure you replenish your energy stores again.
There is so much to explain here but bottom line......eat healthy, keep up the cardiovascular activities to keep the heart and lungs healthy, strength train (or weight lift) 2 times a week to keep the muscles and bones strong (I can't stress enough the importance of this) and you will begin to see your body transform the right way. Your weight is not bad at all so don't worry about it so much. Have your body fat measured and keep that within the healthy range. You'll look fabulous!!