Whether Ms Fan is breaking the law - or merely sidestepping it - with her dairy conversion is a grey area.
She has an interim licence to sell the "legal highs" because she previously sold them through her dairy.
The small room will have a locked door leading into the dairy, and a separate door from the exterior. She said no food or drink would be sold in the room.
Section 52 of the new act says that, in general terms, a premises selling psychoactive products would need to be considered to be completely separate from a premises excluded from selling them.
Ministry of Health Psychoactive Substances Regulatory Authority manager Donald Hannah said the ministry was not commenting on the status of individual applications which were still under consideration.
He said it was expected the status of all licences would be resolved by the end of the month.
"There have been some cases where businesses have decided to convert into sellers of psychoactive substances - however, retailers selling psychoactive substances cannot still sell food and drink."
Dr Hannah said where a licence had been issued, the applicant would have met the statutory criteria and made the necessary declarations.
"The licence details where the business of selling psychoactive substances will occur; that is, the licence is for retailing a specific physical address.
Dr Hannah said if information was false or misleading, or the licensee breached the act, the authority may suspend or cancel the licence.
The authority welcomed information on applicants and licence holders, and would follow up that information.
Currently in Wanganui three businesses in Victoria Ave have licence applications being considered by the Ministry of Health.
They are Stardust Creations, Zhen Sheng Lu's Victoria More Discount Smokes and Aloi Josef Muller of A&V Holdings.