Ms Boyd, aged 27, was last seen in Coolamon, in NSW's south-west, on August 10.

Following extensive inquiries, 37-year-old Samuel John Shephard from Coolamon was arrested and charged with murder by detectives on Tuesday morning.

He was formally refused bail in Wagga Wagga Local Court on Tuesday afternoon.

The latest arrest comes just two weeks after police arrested and charged 19-year-old Wagga Wagga man Anthony Shane Hagan with her murder.

While detectives have been unsuccessful in their attempts to locate Ms Boyd's body, Wagga Crime Manager Detective Inspector Darren Cloake told Fairfax Media police were "confident" with the evidence at hand.

A loaded shortened rifle, believed at the time to be the weapon used to kill Ms Boyd, was seized at the property where the teenager was arrested.

Detective Inspector Cloake said the arrest of both men is a significant development in the case.

"We are confident we have identified all the persons involved in Allecha's murder," he said.

"It's very rare that investigators will charge a person with murder without having located a body, but in this case we are confident that we have obtained sufficient evidence to put a strong case before the court."

Both men will return to court in January.

Police will allege Ms Boyd was murdered at Coolamon between the hours of 2pm and 11.59pm on August 10, the day she went missing.

The arrests have resulted from the formation of a strike force in September to investigate Ms Boyd's disappearance, after suspecting she may have met with foul play.

In September police seized a green Subaru they suspected Ms Boyd used to travel from Wagga to Coolamon on the day she disappeared.

The driver of the car was known to police, but police did not elaborate on their identity.

Ms Boyd, a cousin of current Collingwood and former Greater Western Sydney Giants AFL player Will Hoskin-Elliott, lived in South Australia and Victoria before settling in Wagga Wagga two years ago.

She had recently started working as a chef at the Farmers Home Hotel, and was living in various friends' houses. Most of her extended family are based in Victoria.

She was reported missing on August 22 with her disappearance described as out of character. Her bank accounts, phone and social media accounts had not been touched since then, police said last month.

Since her disappearance her family and friends have remained constantly active on social media, daily calling for any information about her disappearance.

Detective Inspector Cloake said Ms Boyd's family had been informed of the developments, and he hoped the arrests will "go towards them having some of the questions relating to their missing sister and daughter answered".

Detectives are appealing for anyone with information to call Crime Stoppers.

with Marguerite McKinnon