If your sure about the Diagnosis of Psoriasis , it can only be managed well by various medications depending on the severity of the condition at that moment.  Moreover the patient aged 20 yrs needs to be managed weighing the pros and cons of the medication so that her vital organs do not get compromised. Let her consult a dermatologist who will have sound knowledge in treating the condition. By and large using emollients daily will keep the skin soft and supple. UV rays has beneficial effects . keeping stress under control is also very important. Infections if any should be treated as well .