I just can't give the owl theory any credence at all. I'm sure Peterson himself has said he doesn't believe it either. I think when people hear about the feathers, they think of the ones we see in pillows or cushions. The actual feathers are microscopic, invisible to the human eye. So small, that a renowned ornithology expert from the Smithsonian could not identify them from any particular type of bird. As far as I'm aware, they've never even been tested for bird DNA, therefore they've never even been identified as owl feathers at all. They could be pigeon, sparrow, anything.
I have wooden stairs, and they attract all kinds of detritus like a witch. I can guarantee that if I put water on my hand, a forensic expert would find microscopic feathers on it, along with all other kinds of animal and insect matter.
Her injuries in no way resemble other injuries from bird strikes. No puncture wounds, etc. I am almost certain that the feathers were picked up from where she was sitting outside, or picked up from the stairs, by sticking to her blood. An owl would've left more than 2 tiny, microscopic feathers.
She was killed by a human, most probably her husband. If not him, one of her step-sons, and least likely, by an intruder.