There are many reasons for white patches.. from idiopathic guttate hypomelanosis to post inflammatory hypopigmentation to even vitiligo. Without examination it is very difficult to diagnose. So don't worry and visit a dermatologist near you. The doctor will examine her properly and treat her as per the diagnosis made. She will certainly benefit .
Thanks for the query.
This presentation can be seen with many skin diseases. The best option is to consult a Dermatologist in person to understand the problem and get it diagnosed. A proper treatment can then be started. Discuss the situation and hope it will be cleared in few days. Don't delay the appointment. You can use a bland moisturiser till then and OTC anti-allergic medications. It could be something which can be ignored to something to be taken seriously, so meet a Dermatologist for proper guidance.