Perhaps the most important question to ask about Fenichka is whether or not she is a major or minor character. Fenichka has a fairly large role in the novel because of her relationship with Nikolai. Later, she is the main reason that Pavel Petrovich challenges Bazarov to a duel. Yet because of her awkward position – the servant-girl who has fathered a child by her master – she sometimes seems to float in the background of the story.
Fenichka seems to be endowed with good common sense and is not without personal pride. Her attitude toward her relationship with Nikolai might best be summed up by the narrator's description when she comes out to serve Nikolai, Arkady, and Pavel tea. As she pours, she becomes confused and blushes. "She looked as if she were ashamed to have come in, yet at the same time somehow felt that she had a right to come" (5.1). Until the very end of the novel, Fenichka occupies this weird in-between space. She knows that she is not fully accepted as Nikolai's companion, yet she feels that she has a right to be.
For these reasons, her relationship with Nikolai is strained. He is a kind man and wants to do right by her, but in several situations we see him act more like a master than a lover. When she comes into his room as he is thinking of his wife, he dismisses her as if she were just another servant. At that moment, Fenichka makes him sad; "Her voice was an immediate reminder of his grey hairs, his age, his life now..." (11.8). Practically, Fenichka has become a replacement for Nikolai's dead wife, yet it is also clear that he thinks of her differently. Whether because of their class differences or because of affection, she cannot be on the same level as his first wife.
After the duel, when Pavel questions her love for Nikolai, she exclaims, "If I did not love Nikolai Petrovich I would have nothing to live for!" (24.147). The quote is clearly sincere, but it is, perhaps, even more honest than it is intended to be. Fenichka may love Nikolai, but he is also her caretaker. She is dependent on him and, if he were to abandon her, she would quite literally "have nothing to live for." Fenichka seems to be keenly aware of this throughout the novel and it is hard to know exactly where economic practicality ends and love begins.
A last point: Fenichka is described as if she were completely ignorant of how her relationship with Bazarov could be dangerous. When he kisses her, she is shocked. She feels little guilt over the duel, and when Pavel points out to her that he saw the two of them, she cries that she is not to blame. The narrator, like Pavel, clearly agrees with her, and the story ends with her happily married to Nikolai. As critical readers, though, it's worth asking if she really was blind to Bazarov's attraction: what might Bazarov have to offer her that Nikolai does not?