If I look at some table of conditionals, such as one here, all past conditions are considered unreal.
But a past condition easily can be quite possible. For example, when the speaker simply doesn't know what actions were done or how they were done and is speculating about the possible variants.
Imagine the situation: You don't know which way was chosen by your friend, but depending on it, there could be different consequences. And you say something as:
did chosethe left way, she could have met the wolf and it is because of that she is not here yet.
But if she
did chosethe right way, she could have met the woodcutter and now she is not here because of him.
Of course, both conditions here are bad, and I do not know how to write them, and the grammatical tables won't help. Really, I am not sure about the second halves, too.
I think, that it should look like the first conditional, only moved to the past, but the logic won't work here...
Disclaimer: Notice, it is not The Past Real Conditional, mentioned here, for
it describes what you used to do in particular real-life situations.