So yeah, the blue line would be the most direct route from Surat to Roma, which is allegedly where she was last seen by her boyfriend. Yet it appears she didn't continue on that route. Perhaps she realised she left something behind either in Surat, or somewhere along the Yuleba-Surat road if she traveled that way, and tried to retrace her steps?
If she intended to go straight home from Dalby to Roma, the shortest route is 268km and takes about 3 hours, 1 minute. The other suggested route (from Google maps) is 287km and about 3 hours 12 minutes. Much of a muchness is the big scheme of things. Condamine, where she stopped for fuel, is on the slightly longer/slower route. If her next destination was Surat, the most direct route is 126km, which takes about 1 hour, 26 minutes, covers about half of the Yuleba-Surat Rd, and looks to travel through Yuleba State Forest. The other suggested option is 145km and takes about 1 hour 36 mins. Again, not a huge difference. Surat to Roma has the one suggested route - Carnarvon Hwy, which is 79km and roughly 53 minutes.
This brings us to why, after leaving Surat, did her car end up on the Yuleba-Surat Rd near Noorindoo, especially if she was allegedly well on her way home? Was the intention to head right home, or was she planning other stops and/or detours?