What type of mange did she have? Are you sure she is clear? If it was demodex mange, it CAN reoccur.
You can add some Fish Oil to her diet to help with dry skin. How often do you bath her? Don't use any conditioner and make sure your rinse the shampoo very, very well.
You can buy some baby premie cotton shirts to help protect her skin from environmental allergents, and to protect her skin from her nails scratching.
Children Chewable Benedryl can be given to help as well. My Roxy is 5 lbs, she get 1/2 tablet 2x a day.
BUT if she has demodex and it has returned, you need to see the Vet