I am afraid I am not the best person to answer these questions, especially as I cannot examine your mother. In regard to the timing of the surgery, this is best answered by a surgeon who has examined your mom. In general, surgery should be a strong consideration if the wound is not healing(or worsening) because, when untreated, it can worsen to include the underlying bone and cause serious infections.
The physical therapist is the best person to ask for ways to get your Mom moving in a safe way that does not put her in any danger.
I am sorry I could not offer more specific suggestions.