Itching is often caused by a histamine reaction, and antihistamine medications are common remedies. Even if it's not an allergy, antihistamines can relieve itching sensations from dandruff, itchy scalp, hives, eczema etc.
No... she is trying to cure your itchy scalp. I take it you have had absolutely NO luck with it? It isnt working?? She went to medical school for a long time... and did a dermatological residency. She might actually know what she is talking about. Keep using it and if it doesnt go away... go back and let her know this.