Isn't "hi'n" a contraction of "hi yn"?
It is, but yn is not contracted when, as here, it is used as the preposition meaning 'in'. This is explained somewhere in the course notes.
What does "in work" mean? "At her place of employment, doing her job"? (For which I would use "at work".)
Here, 'in work' = 'at work'.
Hints really buggerdd this one up for me