Visit Hongkong for Vietnamese Citizen

Hello,

my girlfriend which has a Vietnamese Passport stays in the moment in Thailand with a 30 Days Tourist Visa. She wants to visit me in Hongkong/Mainland. Now I've got the information that Vietnam People need a Visa for Hongkong also. Where can she get it? Has Hongkong an own Embassy or must she apply at the Chinese Embassy? Same documents necessary? Can she apply it in Bangkok with her Tourist one? I am from Germany and have a 6 month Business F. I am already in contact with an office in HKG, she can get there a 6 month one without problems. Thank you