As Sofia Rosa was making her bid on the home turn, Kathy O'Hara was thrown from her mount Single Gaze as they raced towards the back of the field.
O'Hara was reported to be conscious when treated by paramedics before she was placed in an ambulance and taken to hospital with a suspected broken collarbone and possible chest injuries.
Trainer Nick Olive feared the worse immediately after the incident.
"Talk about highs and lows," Olive told smh.com.au. "It probably was my worst day ever when it happened, but now that things have settled I'm feeling quite relieved more than anything.
"I thought the worst, and that's probably why I feel a little relieved now, I kind of feel like 'thank Christ for that', what a relief that everyone is alright.
"I have never experienced that sort of feeling, everything went into slow motion and I just kept waiting for Kathy to sit up, and she didn't.
"When I caught up with the horse she looked OK on face value and then I got to Kathy, and to see her like that, it just broke my heart.
"I've never experienced that before, and all Kathy was doing was calling out my name saying 'Nick, Nick, how's the horse, how's the horse?' and her passion for this horse and the wait and to see her hurt so bad, it tore at the heart strings."
Single Gaze remarkably trotted away from the fall despite landing heavily on her head and neck.