Gregory was found dead in her home on Khandallah’s Baroda St on January 24.
A post-mortem indicated she died due to a “violent act”.
Gregory was described as a “kind and caring friend to many”.
“This is a significant development in the investigation and our thoughts are with Helen’s family at this time,” Det Snr Sgt Tim Leitch said of Monday’s arrest.
“Police would like to acknowledge the response and support of the community during the investigation and urge anyone who may have information and has not yet contacted police to do so.”