GoodSAM responder Lockie Shaw and Ambulance Victoria (AV) paramedics arrived soon thereafter and administered 14 shocks with a defibrillator, which brought Ms Beattie's heartbeat back.
Almost five months since, the 55-year-old was reunited with those who saved her.
"I'm just lucky," she said.
"I'm really grateful they were able to come so quickly."
It was a special reunion for Mr Shaw, who had attended other GoodSAM alerts without a positive outcome.
"I've responded to six others, but unfortunately everyone's passed away," he said.
"It's the best feeling to see that Brenda survived."
Mr Shaw said his experience as a volunteer firefighter led him to join GoodSAM.
"My brother showed me the app and I decided to sign up as I already respond to emergencies every day," he said.
"I like helping people and I enjoy giving back to the community."
AV Mildura Senior Team Manager, Bronwyn Lambert, said Ms Beattie's case shows the importance of early intervention in the chain of survival.
"For every minute that CPR is delayed, a cardiac arrest patient's chance of survival decreases by 10 per cent," she said.
"That's why it is so important that bystanders begin CPR and use an Automated External Defibrillator (AED), if available."
Ambulance Victoria's Shocktober campaign, which runs through the month of October, aims to improve cardiac arrest survival rates by encouraging more Victorians to register as GoodSAM responders.
"GoodSAM is a life-saving smartphone app that connects Victorians in cardiac arrest with members of the community who are willing to start CPR in the critical minutes before paramedics arrive," Ms Lambert said.
"You don't have to have to be first-aid qualified or have a medical background to sign-up and save a life, you just need to be willing and able to do hands-only CPR, be over 18 years of age and have access to a smartphone."