I am gonna conjecture. I have no inside knowledge and I am just taking a guess on some clues so I am more likely to be wrong than right.
Apparently, Rae said she felt a pop when she landed; the trainer was checking the area behind the knee and did not seem concerned about an ACL. Rae has gone from crutches to walking around in about a week.
All that could be consistent with a small meniscus tear. When a tear occurs on the outer third of the meniscus (where there is good blood flow), the tear can potentially heal on its own (sometimes they do and sometimes they still require a surgical repair).
If it is a tear, I am betting that the medical staff has concluded that it has a decent chance of healing in 4-6 weeks (and if doesn't then surgery becomes something to consider more seriously). So, Rae could be back around late December or January, if this conjecture were to be accurate.