Dibaba has no chance whatsoever with a fresh Ayana. But then this is her best event considering she only ran 14:41 in the 5000m which puts her completely out of medal contention. She will therefore put her best effort here for a chance at bronze at best.
Vivian too is PROBABLY no match for a fresh Ayana in either the 10K or 5K. I say probably because the Vivian we saw at the Kenyan Olympic trials was at a whole different level than she has ever been in her entire running career. Her 15:01 win over 5K, beating Hellen Obiri (fresh from 14:32 PB) by over 12 seconds was such a great accomplishment and perhaps the best performance of the entire trials, considering she did this after putting on a solo display of front running to win the 10K the previous day over a stellar field by almost 30 seconds. Her 5K time was the fastest ever on Kenyan soil. And she accomplished all these at 7000 feet above sea level. Experts(ask Ventolin/Calculo) equate her 5K time to velow 14:20 and 10K time are approximately 30:00 at sea level. Given that Ayana is on that kind of level when fresh, I highly doubt she can double back and run a sub 14:40 after a possibly sub 30 performance over the 10K. The fact is Ayana will not have a walk in the park as she has done in all her previous races this year. Kenya's Alice Aprot, though a new face on international scene, features the same characteristics(race strategy) and is just as enormously talented as Ayana. She is the kind of girl who will push Ayana to her "knees"(to the limit). If somehow Ayana wins( I put at 60% chance), she will DNS(90% chance) in the 5K. Aprot has nothing to lose since she is only running the 10K so she will give her everything. That brings us back to Vivian. Since Vivian is doubling back in the 5K and the only one who would prevent her winning the 5K gold is Ayana, I would think she will be "conservative" in the 10K, let Ayana and Alice Aprot "counter-kill" each other and chase bronze and upgrade it to silver in case one of the two DNFs or "dies" out. She will just stick with Dibaba and outkick her at the end, which she would still need a sub 30:15 effort. Then a few days later, she will line up and go for Gold in the 5K. That is my take. Both the women and women 10000m will be the best ever and can't wait to watch them live.