"His right hand held the knife while his left hand held a flashlight.
"She was under threat of knife that she could not make a sound."
The woman was treated at a local hospital and returned to Perth with her family on Sunday.
Police said that the woman's description of her attacker matches that of a man believed to have carried out previous rapes.
A number of people were involved in the robbery.
"They entered the villa by jumping on to the wall," Mr Reinhard said.
Three iPads, two mobile phones and about A$150 in cash were stolen.
It is the latest in a spate of violent incidents in an area of Bali popular with tourists, especially Australians.
In March, Mercedes Corby was bashed by a gang in Kuta as she returned home from a party.
The older sister of convicted drug smuggler Schapelle Corby needed minor surgery after suffering a broken nose and bleeding to the cornea during the assault.
In January, a West Australian man was stabbed multiple times in the back while fighting off armed robbers at his Bali villa.
Bali's Governor Made Pastika said at the time he was concerned that the island's image as a holiday destination was being tainted.
- AAP