According to their Facebook pages, which feature photos of the couple with Ms Haley's young son and daughter, the pair had been in a relationship since August 2014.

Ms Haley, 29, was found dead by emergency services at a property on Fairfield Crescent in Diggers Rest about 11pm on Friday.

Mr Robertson was arrested in Sunbury just before 1am on Saturday morning near Wilsons Lane, Sunbury, about 10 kilometres from the address.

Distraught friends have paid tribute to Ms Daley on social media.

"My heart breaks for your family ... and most of all my heart beaks for such a beautiful person and mother gone too soon and so unnecessarily," one friend wrote on Facebook.

"I will miss your face and all our nail dates, RIP forever beautiful. Katie Haley shine bright."

Ms Haley worked at Castello's Victorian Tavern in Gisborne, but previously worked as a hairdresser.

On Saturday, her family said they had been touched by "an act of pure evil".

"She did not deserve what happened to her," a statement from the family published by News Corp said.

"Our beautiful Katie girl, not only did we lose a much-loved daughter and sister, but two precious children lost their beautiful mother."

with AAP