If character, with at least one force point, attacks Kreia and rolls a 1 can they use a force point to re-roll that attack?

Yep, becuase all that matters is the final roll. Same with Vader CotS, if they are under his influence they can reroll and either hit or be defeated (which may be better than going to the "dark side")...

This is also located in the user comments of Betrayal in the Archives.

thanks!