Why doesn't Christina Rosetti's work as a whole "resist classification of women" in Pre-Raphaelite art, according to the editors? As they write, "A consciousness of gender often leads her to criticize the conventional representation of women in Pre-Raphaelite art, as in her sonnet 'In an Artist's Studio' (1896), and a stern religious vision controls the sensuous impulses typical of Pre-Raphaelite poetry and painting." Please explain this to me using down-to-earth terms. How does this relate to her poem "Goblin Market," if at all?

The two quotations provided about Christina Rossetti’s work regarding women in Pre-Raphaelite art seem to contradict each other. The initial question posed suggests that, according to the texts you read in class, Rossetti does not resist “classification of women.” The second quotation states, however, that she does “criticize the conventional representation.” Your assignment suggests that Rossetti criticizes what is “conventional” but does not completely replace those conventions with unique portraits of women; instead, she still supports the dominant classification of women, one that was most likely imposed by men.
The challenge of the assignment, therefore, is to analyze the two Rossetti poems in terms of the way she represents women and determine if these representations fundamentally challenge other Pre-Raphaelite writers’ or painters’ representations.
In the poem “In an Artist’s Studio,” Rossetti focuses on a single model that a male artist paints in a number of different paintings. This poem is considered to describe her brother, Dante Gabriel Rossetti, and Elizabeth Siddall, who was his model in countless paintings and later his wife. The artist paints the same woman in many different guises. His concern with her is glossed as “feeding,” suggesting that he consumes her as much as she nourishes him. The man, rather than the woman, is the subject. She remains “hidden” and is never represented as herself but only in the roles he chooses:

Not as she is, but was when hope shone bright;Not as she is, but as she fills his dream.

The poem can be read as a criticism of the male gaze, a system in which the man is subject and the woman an object. However, it can also be read as reinforcing, rather than resisting, that classification. Resistance might have taken the form of a poem in which the artist is female and the model is male.
“Goblin Market” does have two female protagonists, Laura and Lizzie. The male goblins call out to them and tempt them with countless luscious fruits. The young women differ in their attitudes to the goblins’ alluring voices and the goods they display. Lizzie urges caution, telling Laura not to look at “goblin men,” but Laura enjoys looking; she wonders at the rich, ripe fruits:

How fair the vine must growWhose grapes are so luscious.

Despite her sister’s warnings that the goblins’ “evil gifts would harm us,” Laura cannot resist. She goes out and meets the goblins, and succumbs to temptation. Paying with a lock of hair, she indulges in “sucking” their luscious fruits until her lips are sore. The next day, when they go out together, Lizzie hears the voices calling but resists, while Laura can no longer hear them; without the fruit, she wastes away. When Lizzie goes out to buy fruit for her sister, the goblins torment her and try to force her to eat; she manages to hold them off but cannot get any fruit. Back home, Laura is grateful for her sister’s devotion; even without the fruit, she gradually recovers her health.
Many years later, when the two are wives and mothers, they reflect on this episode and how Lizzie saved Laura.

For there is no friend like a sisterIn calm or stormy weather;To cheer one on the tedious way,To fetch one if one goes astray,To lift one if one totters down,To strengthen whilst one stands.

With this message of female solidarity, it seems that Rossetti is promoting the value of women’s friendship over the sexual relations between man and woman that are clearly represented by eating fruit. Here again, however, the poem can be read as upholding patriarchal values rather than resisting conventions. Desire is glossed as male and evil, while purity is portrayed as female. Sexual desire is not appropriate for women, Rossetti seems to suggest; Laura has “gone astray.” Instead, women are seduced and abandoned by duplicitous males. This depiction of sex roles is entirely conventional and supports the interpretation that Rossetti is not resisting the dominant classifications.
https://www.poetryfoundation.org/poems/146804/in-an-artist39s-studio

https://www.poetryfoundation.org/poems/44996/goblin-market