just jumping off your post with information from the autopsy to ask:
How does the owl theory explain the "fracture with hemorrhage, superior cornu of left thyroid cartilage"? (page 2 of autopsy)
I am not a doctor, so I am just thinking-out-loud here, with no real knowledge besides from what I have read. So feel free to correct or expand on!
To get the neck injury in the Owl scenario, it could be explained as it would in the fall theory: falling/slipping/passing-out and her neck/head impacting a blunt object - in this case, a step. So in that scenario the head lacerations were from the bird, and the neck injury from the subsequent collapse.
Fractures of the upper thyroid horns are a frequent finding after a variety of neck injuries resulting from a direct mechanical trauma, e.g. compression of the neck in manual strangulation or ligature strangulation, from blunt injuries (falls or blows against the neck), and sometimes from indirect trauma (whiplash-injuries). Although it is well known that thyroid horns can be broken with relatively little pressure, no quantitative data are available in the literature.
Interestingly she didn't really have any other injuries to her throat, besides the abrasion on the right side.
But here's a case of a man collapsing, at standing height, from heart failure, who fractured both superior cornu of the thyroid cartilage, without any other injuries to the neck area.
A 45-year-old man collapsed at a fairground and died after unsuccessful resuscitation. He showed excoriations at his elbows and right knee, a crush injury at the mentum and his mandibular front teeth were knocked out. The upper parts of the chest and the head showed blue discolouration as a marked sign of congestion due to heart failure. The right coronary artery (RCA) was completely obturated by a 5 cm long post-stenotic thrombus with subsequent myocardial infarction of the lateral part of the left ventricle. Both superior horns of the thyroid cartilage were fractured with surrounding haemorrhage, the skin and muscles of the neck uninjured.