Hi, Welcome to HealthcareMagic Forum.
I can understand your Concern, give her Oatmeal baths in lukewarm water which will form a comfortable coating on her skin. Take her to a Pediatrician
as she needs to be examined so that the Doctor can prescribe her anti histamine
topical lotions which will reduce her itching. Trim her fingernails very short so that continuous scratching does not lead to secondary infections. if she is a otherwise healthy child she may not need any anti virals else she will need it. Let her avoid playing with other children until the blisters subside. Give her home cooked fresh protein rich food which is bland, easy to swallow and digest. Let her avoid salty, highly acidic junk foods. Let her take planty of fluids and get adequate rest.
I Wish her Good Health, Take Care.