The most likely inference from these sentences is that Ann Eliza is option c: unconcerned about stylish clothes.
The elder sister's question, "What do I need, I'd like to know? Ain't I got a best black silk?" suggests that she is already quite satisfied with her wardrobe and does not need anything new.
Ann Eliza's silence and lack of protest when her sister rejects her offer of a new dress further supports this inference. This suggests that Ann Eliza is not only aware of the quality of her clothes but also takes pride in having stylish items, as indicated by her mention of the "best black silk."