Is the first sentence ambiguous? In the grammar comment for this sentence they said it means that the speaker is making an assumption that the woman hasn't left work yet. Keeping in mind another meaning of should have left (that it was desirable for her to leave the office), can we say that the meaning of the first sentence can be either and depends on the context?
She shouldn't have left work yet. (I'll call her office.)
Here is one more similar example:
He shouldn't have boarded his plane yet. We can probably still get hold of him.
If I were a native speaker of English, I would never shut up. :-)
You are correct. It all depends on the context. In both the contexts shown, the assumption meaning holds good.
I'm not a teacher of English, but I have spoken it for (almost) all of my life....