Detective Superintendent Jayne Doherty from the Child Abuse and Sex Crimes Squad said the pair had allegedly matched on a dating app.
She told reporters on Sunday they communicated on various platforms, including video calling, before meeting up on Wednesday.
Gunathilaka is alleged to have met the woman for prearranged drinks and returned to her home, where the sexual assaults allegedly occurred.
“This woman took a lot of steps to ensure she was safe,” Detective Doherty said.
“She met up in a public place, with other people around that were aware that she was there to meet someone for a date.
“It’s just unfortunate.”
A crime scene examination was undertaken at the address on Saturday.
It is understood the rest of the Sri Lankan team has already flown home without Gunathilaka.
“The male is being supported by the Sri Lankan consulate,” Detective Doherty said.