On current fitness, there are 4 runners in the final - St. Pierre, Schweizer, Andrews, and Cranny - who could reasonably hang if Valby runs 14:50 from the front. Given the nature of the 5k, it's a fair to say that at least one of the 4 will be off their game tonight and fall off the pace. However, there's another 3-4 runners - Infeld, Donaghu, Smith, etc. - who have shown fitness at some point to indicate they COULD run 14:50. It's possible that one of those runners could stick with the pace, bringing our lead pack up to 5ish (including Valby). Importantly, every second dropped could be another runner dropped. 14:50 and maybe we have 5. 14:45 and maybe we only have 3, and Valby goes. So while front-running is risky, if Valby has anything in the tank to drop 5-10 seconds it could basically guarantee her spot.
Whereas if Valby does ANY sitting back, I think she just makes it harder for herself. Her best distance is the 10k, even by the time you get to 3k she starts to fall off. Going from 2-4 laps out is simply not going to be enough time for her strength to matter. Is she really going to beat 3:59/4:00 women over the last mile? Given she has solo'd 14:52 twice this season, and ran a good portion of her 30:50 race alone, I think her chances of running 14:45 from the front are higher than her chances of out-kicking any of her top competitors in a 15:00+ race. Front-running FTW!