The way she stood over her was a woman’s stance to me. She’s a tall(er), what we would call “thick”, or “big boned”, not heavy set woman, IMO.
I like your impression of "big boned", but not "heavy set". I would possibly add 'athletic" to the description as well.
The murder appears to be light on her feet when both approaching the victim, horribly standing over her, and running away.
When running, she (at least an apparent 'she'), does not seem to assume the instinctual and less efficient feminine running stride of hands down by the hips and crossing over the hips with a shorter stride. Rather, she seems to take the faster and more efficient "male" running stride.
The apparent athleticism can be natural, but the possible "male" running stride could well have been taught. One of the first things coaches do with young girls is to instruct them to run like boys and break their natural feminine stride / arm motion habit.
This could suggest that the murderer played sports as a youth and / or in high school. If so, perhaps she continued to participate in an adult recreational league? Though I do not want to read to much into it, softball has a certain number of big boned, but athletic females who would not be described as "heavy set".