In Chapter V of Ethan Frome, what real conversation are Ethan and Mattie having when they speak of marriage?

The conversation about marriage between Ethan and Mattie
during their one evening alone is full of emotional connotations since they are not free
to express their real feelings about the subject or each other. When Ethan tells Mattie
he had seen "a friend of yours getting kissed," they begin to speak of Ned Hale and Ruth
Varnum, a young Starkfield couple.

Ethan observes Ned and
Ruth will probably marry in the summer, and then with "a pang" of emotion, he says that
next it will be Mattie's turn to marry. Mattie laughs a bit "uncertainly" and asks Ethan
why he continues to bring up the subject of her getting married. Ethan responds, "I
guess I do it to get used to the idea." Underlying Ethan's words is his recognition that
he has no claim on Mattie, but Mattie's thoughts immediately turn to Zeena, wondering if
Ethan's wife "has anything against me."

In their ensuing
conversation, Ethan and Mattie discuss Zeena's behavior and her attitude toward Mattie.
It is the first time they have talked "so openly" about Zeena's feelings toward Mattie,
and together they look for any sign that Zeena has grown to dislike the girl. Ethan
assures her that Zeena has said "not a word" to him. Mattie
replies:

I
guess I'm just nervous, then. I'm not going to think about it any
more.

Ethan agrees, with
sudden heated emotion, "Oh, no--don't let's think about it, Matt!" Unspoken between them
is the fear that Zeena dislikes Mattie and will send her away. The prospect of being
separated is unbearable for both of them, although they cannot express it
openly.