In "The Wife's Lament," how is interiority represented?

Great question! In literature, interiority is often described as a character’s internal thoughts, feelings, emotions, and struggles. Interiority is a major part of what makes characters compelling. Access to a character's inner thoughts is engaging and relatable for an audience.
"The Wife’s Lament" is an Anglo-Saxon elegy that narrates the misery of a woman who has lost her husband. The poem is unique in the Anglo-Saxon canon because it is so introspective. Rather than narrating and celebrating the deeds of heroic men, the poet describes the anguish of a woman mourning her life of solitude.
Although the narrative background of the poem is vague, the events described by the female speaker of the poem are poignant. The speaker reveals that she has been ordered by her “lord” to settle in a foreign place without close friends. However, she finds a “well-suited man” and falls in love. Many scholars argue that the “lord” and the “well-suited man” are the same. This common interpretation means that the speaker of the elegy is of high social status, as she would have been married to the chieftain or tribal leader. Examine how the speaker treats the early days of her love:

Keeping cheery, we vowed quite oftenthat none but death could separate us.
That soon changed . . .

This reflective tone is fascinating because it reveals a touch of bitterness in the speaker. Her relationship with her husband was genuine and loving, but it did not last. The woman is conflicted as she remembers her former husband.
The remainder of the elegy describes how the speaker was “anchored” to her home and abandoned by her husband. She refers to her home as a “bitter hovel” and a “shelter without joy.” This introspective language demonstrates that the speaker is deeply unhappy with her lot in life. She speaks of her lover's “disappearance,” but the exact circumstances of her abandonment are unclear.
In addition to the loss of her husband, it appears that most of the speaker's friends are also deceased. Look at how the speaker describes spending her days:

All my friends’ dwell in the dirt, I loved them while they lived, now guarding their graves,when I go forth alone in the darkness of daybreakunder the oak-tree outside this hollowed earth.

This picture of a lonely woman yearning for human friendship and love is amplified by the interiority peppered throughout the first-person narration of the poem. The speaker floats from thought to thought; she reminisces fondly about her husband in one line and lambasts him in the next. This style grants the poem’s audience access to the battle raging in the speaker's mind and heart. In a sense, this entire poem is a poem of interiority! "The Wife’s Lament" is famous and celebrated because of this unique window into a woman’s loss and isolation—a rarity on multiple levels in Anglo Saxon literature! I hope this helps!