Look at that, a little earlier and you could have used it for the 10 challenge too ;-) I thought about doing a birthday candle shot - my husband just turned 40. But that's a lotta candles - would have called it 'conflagration'. Happy Birthday to the birthday girl. Was it your daughter?
So you're probably getting marked down by a lot of people since it's a candid.... but I think it is a fantastic candid. I love the colors and the lighting. Gives it a very lively feel, which is appropriate for a party. I like the interesting angle that you chose for the cake. I think you did a great job with the timing of the shot, having some candles blown out and others still lit but obviously being blown out. I do not mind at all that the head of the person is cropped out, and I actually sort of like it this way (more focus on the cake, and therefore the "fire", and less focus on a particular person.)
Nice to see an original concept in the challenge, congrats on being the only one to think of it, obvious though it may have been! The composition is a bit cluttered, I think. The person standing behind her is distracting, the angle isn't the best. I would like to see her face as she's blowing the candles out.
Fun! Happy Birthday! But on the image side. To me it looks like a snap shot and the background is much to detracting for the flames to be presented powerfully. It has fire so I will give it a 5 but just barley.