Short answer, no.
Long answer, maybe? She's has shown her sex, which is a sign she is about to flower. Eventually those white hairs start multiplying rapidly and the following begins. You will, however, get no solid answer for when flowering begins. When she starts stretching (gaining an inch or two daily) I consider that pre-flower, and flowering begins when growth slows down again. I use this method because it's accurate as far as nutes are concerned.