商業罪案調查科 (Commercial Crime Bureau --"CCB")will not be in charge of this kind of transaction unless the transaction amount is very large, say HK$10M...
Based on my observation of the case, I can assure you that police cannot help you to recover the money in this kind of situation and dispute. Police can never help anybody to recover the money or damage.
For buyer, if you really want to claim for money, I suggest you to file your claim to "Small Claim Tribunal" (For amount below :HK$50K) and also Claim for her "Mis-representation". When court finalised a judgement, you can formally request her for the money. If they still refuse to repay, you could file bankruptcy petition on her.
You can still file your case to police but they cannot do anything based on my actual experience and knowledge.