I think you are correct Rosie will lose the tip first since you are seeing increased swelling. Viewed from inside of leg, there is a very clear line of demarcation between necrotic tissue on top of shank, and living healthy pink tissue in the middle. I agree with you she may keep part of her leg below the hock, since the pink tissue in middle of shank appears alive and healthy.
And then from photo of outside of leg, is tissue from blackened tip to just below the pressure sore necrotic too? (I cant tell if the darker color is necrosis or simply her original shank color since she is an Easter egger). The auto-amputation process may take a while longer, due to the complicated "uneven-ness" of the necrotic vs. healthy tissue on her entire shank. I know you mentioned at least once in this thread you tend to be impatient by nature. I think after Rosie's auto-amputation and healing process is complete, you will have exhibited more patience than you ever thought you had in you.

. Yes the auto-amputation process is very interesting, but sadly signifies a severe injury and eventual loss.
Next time you post, include a picture of her pretty Easter egger face too. (Or is molting?) A photo of Rosie's cute cheeky face is a good reminder that the reason you are enduring this lengthy process is because Rosie has a warrior fighting spirit that will remain intact long after the dead tissue is gone. And that is true of you too!