Victoria police have identified the woman as Rachael Dixon, who was born and raised in Southland.
The death of the 53-year-old at the wellness centre in the town of Clunes is being probed by detectives from the Moorabool Crime Investigation Unit.
Officers are examining whether the drink contained mushrooms.
Victoria Police were called about midnight Sunday and believe Dixon became ill after ingesting a drink.
The investigation is open and a report will be prepared for the coroner.
Her son Matthew described her as "the most loving, most caring person I’ve ever known" in a post on Facebook.
"Words can’t begin to describe how much I will miss you, wish I could give you one last hug."
Her sister also expressed her shock and grief on social media, saying "words cannot express the heartbreak we are all feeling".
"Life is so ... short please hug and love those around you."
Ambulance Victoria confirmed paramedics were called to the Clunes property at 11.55pm on Saturday and took two other people to Ballarat Base Hospital.
The retreat describes itself on social media as an alternative and holistic health service.
It advertises multiple services, including facials using "wild foraged plants".
On Friday night, the retreat hosted an event with a medium where guests were given a chance to "ask questions of the spirit communicators".
A planned event described as "sound healing" was cancelled on Sunday.
AAP has contacted the owner of the retreat for comment.
Clunes is about 30km from Ballarat, which has experienced a series of tragic events in 2024.
Three local women, Samantha Murphy, Rebecca Young and Hannah McGuire, have died allegedly at the hands of men in the past two months.
Miner Kurt Hourigan died in a mine collapse in March and the area experienced bushfires over summer.
Less than a year ago, three people died and another was hospitalised for months after allegedly consuming poisonous mushrooms in eastern Victoria.
Don and Gail Patterson, both 70, and Gail's sister Heather Wilkinson, 66, died after eating a meal at the home of Erin Patterson in Leongatha in July 2023.
Ms Wilkinson's husband Ian, who was also at the lunch, spent close to two months in hospital.
Erin Patterson, a mother of two, has been charged with three counts of murder and five of attempted murder.
- Additional reporting ODT Online
