If you are quick you can save her, but not Dr Sova. I spoke to Valentina just after I left the FOB at the start, she gave me info. I drove through Krastonovav and spoke to the good doctor. Then I captured Lagushina, and took her straight to the LZ. As I approached, Valentina tried to drive past, it seems she drives through Krastonovav then through to Gvozdao. I had played this earlier and knew her fate, so I shot out her tyres. She gets out of the car and just starts running in a straight line, I cannot stop her. Anyway I evac Lagushina, so I go back to see the Doctor and he is already hanging. 30 seconds later I get the message that the Doctor is dead, but where it previously stated that Valentina took a bullet to the head, it said nothing. So she lives, somewhere in the world.
I replayed the mission and followed her. She arrives at the sentry point outside of the FOB at around 1045 hrs, not long after you get told about the bombing in Moscow. She then drives through Krastonovav, ploughing through everything in her path. She proceeds to Gorka, straight through. She refuels at a petrol station at 1105. By 1106 she has completed a full circle and is back where you first meet her, outside the FOB sentry. She keeps doing laps. This raises a question: if she never disembarks, how does the lynching in the area affect her? It is presumed that she is pulled over and shot (a trigger is in place to kill her in her vehicle) I say this because after I disabled her car the first time and she got out and ran (straight to Gorka, her next waypoint) she wasn't killed. In conclusion, either she is meant to die, or you are able to save her by forcing her to run. I think that's unlikely, but it's all I've figured out.
Another point to note is that at around 1103 when she passes through Gorka, the yellow truck there starts driving somewhere. I didn't follow it, but that seemed odd.
I haven't finished the campaign yet, but I will let you guys know if she appears again....