An unexpected part of the biology of these large spiders is that the female must come to ground to lay her eggs. This is probably most hazardous time of her life since she would be exposed to all sorts of predators, the worst of which is the introduced Cane Toad, Bufo marinus. (I'm an oldie and use the old generic name!!)
Argyrodes minaceus, the Small Thief Spider.
We wish Mrs Nephila success in avoiding the Butcherbird!
There are about 4000 described spider species in Australia but it is estimated that there may be as many as 20,000 species once they are all described, Whyte and Anderson, 2017.
Both "Budak" and Martyn Roninson have commented that the red spiders are actually Pirate Spiders. Martyn further notes that it is the genus Argyrodes. A check in the book noted below indicates it is the Small Thief Spider, A. miniaceus. Martyn further notes that these spiders can steal the prey of the host spider and eventually cause the big spider to abandon its web and seek a new site. And that's exactly what must have happened as she is now not in her web.
Whyte, R., Anderson, G. 2017. A Field Guide to Spiders of Australia. CSIRO Publishing, 445 Pp.