I think buying her a present is a great idea. My mom always told me, “Never be afraid to do something nice for someone.”
It doesn’t have to be expensive, it’s the thought that counts.
Ask someone who works in her office or clinic if it’s alright to buy her a present so you know for sure. (but tell them not to ruin the surprise).
One psychiatrist told me that the rules at his clinic say you can buy a food/candy/cookie etc. gift for your therapist or doctor but nothing material.
I bought Christmas presents of food for therapists in the past and they liked it. It’s a nice gesture and most people like getting gifts and most people like getting food gifts and psychiatrists are people.