Plot hole: Sarah turns up on the bridge to fight the Rev-9, we later learn that she is texted the location of where to be as when the terminators travel though time it causes a gravitational anomaly, and this is where she needs to be. The Rev-9 had been there ages killing Dani's dad etc, Sarah would have no idea to be on the bridge after the terminator has chased them though the town - she can't possibly know that location.
Other mistake: After the final battle, the protagonists simply leave the scene and the remains of the T-800 and Rev9 behind. Sarah should've known by now that letting even the smallest part of a Terminator to be fallen into bad/incompetent hands could lead to disastrous consequences for the future of mankind. Being obsessed and even paranoid about future and fate, it's very unlikely that she could just go away like that, calling it a day before destroying all the present time traits of the Legion.
Suggested correction: Sarah knows that both machines have been destroyed by Grace's power source. Or she may have simply retrieved any leftover parts off-screen.
Suggested correction: Sarah is very skilled at fighting Terminators. She receives the coordinates but knows that many other real-world factors may impede her progress to those coordinates, so she makes efforts to prepare for that. Also, the coordinates that she received for the Rev-9 may very well have told her to fight it on the bridge because the T800 who sent those coordinates knew that Sarah would also then be able to rescue Dani and Grace, and eventually meet up with him as a result.
I'd say the real reason Sarah is on the highway to fight Rev-9 is that she followed it. She misses the moment it arrived (from the future), she follows it to the car factory, but she misses it again, then she finally catches it up on the highway.
It is explicitly stated by the T800 Carl that he was sending Sarah the coordinates of where the terminators would appear, because the arrival would create a space-time wrinkle he is able to measure ahead of time. There is no indication he can predict the future events and send Sarah coordinates of places to be other than that.
Epigenis
Suggested correction: Sarah's truck can be seen in the background when Grace arrives. Grace doesn't look like any Skynet Terminator, and the time bubble she arrives in is different to the ones in T1 and T2. We can infer that Sarah followed Grace from her arrival to the bridge in an attempt to understand what was going on with the new time travellers before intervening.