Transit fligt via Hongkong

My sister is in San Fransisco and visiting SL for a short holiday. She is Sri lankan passport holder but has PR in US. She has already booked seats in Cathay Pacific flight. When Returning from CMB to San Fransico she has to spend more than 12 hours in Hongkong according to flight schedule. Is she need to apply visa for that? if so can she apply for it from CMB ? how long will it take ?