Feminine for Guru गुरु

A friend said to a female colleague, "You are the new guru in this field." Is there a female equivalent of the word "guru"? 

It is perfectly accepted in common usage, to call even a female as "Guru". But if one wants to be particular, there are some suggestions in:

Guru Ma  (गुरु माँ), 

Guruuaain (गुरुआइन), 

Guru Patni (गुरुः पत्नी), 

GurvI (गुर्वी)