Possible Clues:

• Is coming at the double from Egypt to Oxford
• Two lives on river
• Beloved of Osiris
• Goddess of detached territories?
• A name for the Thames at Oxford and upstream
• Osiris' spouse
• Are, perhaps, a single deity
• Si Si - she's an Egyption goddess
• "It depends on what the definition of ___"
• A dark blue flower of which the iris is typical