After the second time (6months) my friends GF was pulled aside and told 'no more'. They flagged her and said they knew what she was up to and wouldn't be allowed in a 3rd consecutive time. They got married @ City Hall a few weeks later. Whole ceremony took under 2 minutes...
I'd HIGHLY recommend you marry her in HK, give the paperwork to the government for the visa and then throw it away. Don't tell anyone in your families. She'll be a 100K tax deduction for you, and won't have to leave.. in fact she can legally work easily (friends wife got on with telecom company as she was skilled in area back home and now makes 40k a month).