Master? Are they really calling her with "shishou" (which is half teacher, half master) or "goshujin-sama"?
Either way seems like an odd choice of translation. Generally adding the jp suffix untranslated is preferred, for context (and because it just soudns plain weird if forced into english since we
very rarely call ppl with titles that way; that's also why "onii-chan" as a whole is preferred over "brother-chan" or "brother").