The line "one morning two butterflies play in front of our trench"is an example of

Personification

Explanation:

Personification is the act of conferring human characteristics on inanimate objects or on the abstract, such as emotions and animals, for example.  The personification is much explored in literature, especially in stories of fantasies and fables. In this way, the narrative becomes more expressive, dramatic, poetic and creative, qualities that are essential for the construction of an interesting literary text.

In the case of the line "One morning two butterflies play in front of our trench", the personification was used in the attribution of a human characteristic (the ability to play) to the butterflies.

explanation:

you only need simple sentences to answer this. just answer these questions.

what do you think annie thinks of the mother? do you think annie believes the mother is a fit mother for helen.

what about the father? what would annie think of him? she might not like him, but does she respect him.

how about the son? would annie think he is the only voice of sanity in an insane place?

what about helen herself? this is the key question. how does she see helen? what do you suppose she thought her first job was going to be.

these aren't hard questions. just state the obvious. annie is not that well educated: she just knows what she has to do. write it that way.

you can do it if you've read the book or seen the play or movie.