This looks like you applied a selective blur to the non-flower portions of the arrangement. The effect is very nice, but the irregularity of the boundaries is a bit disconcerting.
Wow... busy and colorful. I like the way you met the challenge's "to offset your subject" by making your model the only thing without color. Instead of color drawing your eye to the model... I find my eye flees to her to escape all the color and rest. Since nothing about her holds my attention, though, I visually go wandering again.
Definitely alot of color bursts going on here. I like the subject you've chosen and colors in this shot. IMHO more emphasis on the woman in black may have helped to emphasize the contrasts between her and the background. Maybe a wide angle and tilted composition? Just my humble opinion, nice shot nonetheless