curious if I may impose on the professional health folks on here:

[Backseat Driver]

9. Sepsis is very dangerous, but everyday more about treating it is known;

Blood clotting in the appendages is definitely a possible complication.
Loss of normal blood flow and immune reactions to the infection with coagulation cause necrosis in tissues surrounding a clot. There's a lot of studies one can read through the NIH and PubMed; her doctor and your browser and/or a librarian can help find those studies, so you can better understand the reasons for which her treatment(s) and surgeries are being considered.

Sending calming vibes for you, and my prayers for your sister-in-law's recovery!