Zara’s having a rough course of life and she thinks this is because of her past sins, she is being very depressed and she wants to punish herself so she doesn't ask for any blessing from Allah(s. w.t). Q) what is she missing primarily?

Zara misses the thought about the merciful nature of Allah (s.w.t).

She is missing the thought that Allah is the most merciful who can forgive His sinful person. She has to ask for forgiveness of her sins and blessing from Allah (s.w.t) instead of punishing herself for their sins. The thought of Zara is right that her rough coarse of life is because of her sinful past so in my opinion Zara misses the thought about the merciful nature of Allah (s.w.t).

check your question

i would think its c but i'm not sure