I agree, the bushs and tree create a busy background, with that said it seems like she was placed there. I think a change in location would have made it more appealing and if the subject was atleast 3 feet from any object, she would have been the primary focus. 2 spots missed on her head, and remain b&w.
The tones on the surrounding bushes are nice and, besides parts of her hair, the color selection was done cleanly. I would definetly try a calmer background.
Hmmm... the color of the subject may be a bit strong for a pure color isolation effect. Maybe you should turn down the saturation of the background instead of makinging it absolutely B&W. I think you need some color in the background, but I agree the bushes may be a bit cluttered in the unmodified original.