Rufous Hummer Attacking

She's at it again. I think the cold weather brings it out in her. Late this afternoon, a pair of cardinals made the mistake of sitting on a branch about 10 inches above one of the (of 5) hummingbird feeders that I have out. Immediately, and out of nowhere, the female Rufous Hummingbird appeared making a beeline straight at the heads of the cardinals, over and over, on the attack. What a brave (and dumb?) little bird!