I'm guessing he probably thought their chances of beating the ogre were small even with the three of them. If she manages to teleport away before they got wiped, then at the very least she would be able to come back with hired help and recover their corpses for resurrection.
I think they should have practiced and prepared for scenarios like this. They seem very ill-prepared and not very vigilant for veteran adventurers. First the snake, now an ogre...How do they keep getting caught off guard like this?