I think Wikipedia has it wrong. Go to source instead
http://www.legislation.gov.hk/eng/home.htm and find Chapter 200as referenced in Wikipedia.
Reading that, the target is clearly owners or tenants of premises where ongoing 3P take place, and agents who organise prostitution (2P or many P).
OK it's a little bit grey, since it doesn't explicitly say what is NOT a Vice Establishment ... but IMHO even the most virulent prosecutor would have difficulty making any of that stick to a single occurence where 3 people meet privately under their own arrangement.
Conclusion: as long as it's with you at your place, and your place is not somewhere the girl uses for sex work, you're free from busybodies.
WARNING That's my private opinion for the purpose of stimulating discussion and debate, I'm not a lawyer and have no clue what I'm talking about.
Here are the references in full:-
(1) A person who on any occasion- (Amended 69 of 1990 s. 3)
(a) keeps any premises, vessel or place as a vice establishment; or
(b) manages or assists in the management, or is otherwise in charge or control, of any premises, vessel or place kept as a vice establishment,
shall be guilty of an offence and shall be liable-
(i) on summary conviction to imprisonment for 3 years; or
(ii) on conviction on indictment to imprisonment for 10 years.
and
(1) A person who, being the owner or tenant of any premises or his agent- (Amended 69 of 1990 s. 3)
(a) lets the whole or part of the premises with the knowledge that it is to be kept, in whole or in part, as a vice establishment; or
(b) where the whole or part of the premises is used as a vice establishment, is wilfully a party to that use continuing,
shall be guilty of an offence and shall be liable on conviction on indictment to imprisonment for 7 years.
and
(1) A person who- (Amended 69 of 1990 s. 3)
(a) being the tenant or occupier, or person in charge, of any premises permits or suffers the whole or part of the premises to be kept as a vice establishment; or
(b) being the owner, or the master or other person in charge, of any vessel permits or suffers the whole or part of the vessel to be kept as a vice establishment,
shall be guilty of an offence and shall be liable on conviction on indictment to imprisonment for 7 years.
and
(1) A person who- (Amended 69 of 1990 s. 3)
(a) being the tenant or occupier, or person in charge, of any premises permits or suffers the whole or part of the premises to be used for the purposes of habitual prostitution; or
(b) being the owner, or the master or other person in charge, of any vessel permits or suffers the whole or part of the vessel to be used for the purpose of habitual prostitution,
shall be guilty of an offence and shall be liable on conviction on indictment to imprisonment for 7 years. (Amended 31 of 1997 s. 15)
With the definition
(3) Premises, vessel or any place shall not be treated as a vice establishment for the purposes of this Part unless-
(a) the premises, vessel or place are or is used wholly or mainly by 2 or more persons for the purposes of prostitution; or (Amended 90 of 1991 s. 2)
(b) the premises, vessel or place are or is used wholly or mainly for or in connection with the organizing or arranging of prostitution.