Guinevere, Arthur's queen and Lancelot's lover, lady of Camelot, can't catch a break. Whether in literature or film, she is almost never portrayed with the sympathy granted to either of the heroic men in her life. (I have used the spelling favored by each auther in discussing these characters. I favor Guinevere myself, but the name has been spelled in perhaps half a dozen different ways and this is the case with many, many characters of Arthurian legend.)
In Malory's Le Morte d'Arthur, Guinevere is kidnapped by Sir Maleagant, but when he discovers that Lancelot is on his way to rescue the queen, he begs her forgiveness and mercy, which she grants. Lancelot, in a righteous rage, wishes to kill Maleagant during the rescue, but is prevented by Guinevere. However, when Maleagant rightly suspects that the queen has gone to bed with Lancelot, she convinces her champion to fight her former kidnapper. This combat, the outcome of which decides whose cause is right, is the product of Guinevere's choosing, rather than Lancelot. In Malory's framing of this episode, Guinevere comes in for the most censure. Her vengeance is calculated, in contrast to the Lancelot's fury. Maleagant is, of course, right - the queen has committed adultery with her champion - but both men are depicted as victims of Guinevere's machinations, despite the fact that Maleagant abducted her and only ceded her because he was afraid and Lancelot is at least equally guilty of the adultery of which she's been accused. It's ridiculous to hold Guinevere most worthy of blame, unless she, as a woman, is being held to a more stringent moral code of conduct.
This episode, rarely included in cinematic adaptations of the Arthurian legends, is one of the most brutal in Marion Zimmer Bradley's gynocentric re-imagining. In this telling, Guinevere (Gwenhwyfar, in the Welsh spelling Bradley employs) is brutally raped by Maleagrant, intending to sire a child and therefore compel Arthur to cast her off. This is a key turning point for gwenhwyfar in Bradley's telling. The heroine, Morgaine, warns her not to be fooled by Maleagrant and Gwenhwyfar is thus framed as being foolhardy and rather stupid, in keeping with her character up to that point. After the rape, she gives herself free license to commit adultery with Lancelot, reasoning that if God will not protect her when she prays for his help in resisting a loathed sin, she may as well commit the sins she wants to commit. There are a number of issues with Bradley's text - after Bradley's death, her daughter came forward, alleging that she had been sexually abused by her mother throughout her childhood, and this accusation puts a number of sexually charged scenes in a different light - but I feel particularly troubled by how poorly Gwenhwyfar is treated. In a book that explores with such sensitivity and nuance the often demonized characters of Morgaine and Morgause, even granting Lancelot's poor love-struck Elaine a certain degree of agency, Gwenhwyfar's rough dismissal strikes me as tone-deaf. While the three other heroines (as well as Nimue) use witchcraft to attain their ends and cause men to fall in love with them, sleep with them, or otherwise do their bidding, Gwenhwyfar is herself subject to love. She is resented by Morgaine because Morgaine loves Arthur and by Elaine because Elaine loves Lancelot. In other words, Gwenhwyfar is the victim of unfortunately catty jealousy and slut-shaming.
In the end though, Guinevere is most often reviled for failing to produce Arthur's heir. The "blame" - that is, if one is willing to assign blame for infertility - has to be hers because we know that Arthur is not infertile and neither is Lancelot. Arthur has a son, Mordred, by his half-sister Morgause (or Morgan, depending on the source) and Lancelot has a son, Galahad, by Elaine. Thus, Guinevere, despite engaging in multiple sexual relationships with fertile men, never gets pregnant. In the Medieval and Renaissance worlds, in which childlessness could be publicly ascribed to God's disapproval, infertility can indeed be a significant signifier of a woman's wickedness, but in the relative sexual liberation and the drastic fragmentation of the Christian moral system in the wake of the scientific revolution, industrialization, and numerous civil rights movements, why should we, still, blame Guinevere?
Though T. H. White was not terribly adept at writing female characters in The Once and Future King, ironically he seems to better understand the complexities of any moral judgement on Guinevere, though this is always tempered by a strictly gendered perspective that assumes that women exist primarily in relation to men. On the one hand, he writes that "she had all the proper qualities for a man-eater"; on the other, he very sensibly points out that the two men "whom she apparently devoured, lived full lives, and accomplished things of their own." The difficulty at which White arrives is this: he explicitly recognizes Guenever as what he calls "a real person," that is, a complex character that didn't always act in one, single consistent way and this stymies him because she's a woman and he is accustomed to assuming a person as explicitly male. This in and of itself is a remarkable step for a writer that blithely dismisses crying women as "repulsive" and angry women as "revolting." White also recognizes that Guenever's childlessness is at the heart of her trouble and he even goes so far as to feel pity for her condition as a woman. While Arthur and Lancelot busy themselves with warfare, adventures, the administration of the Round Table, and the search for the Holy Grail, Guenever is stuck, bored to death, at home and "unless she felt like a little spinning or embroidery, there was no occupation - except Lancelot." White's compassion for Guenever prevents him from indulging in the moral condemnation of Malory or the haughty dismissal of Zimmer Bradley.
White's compassion for Guenever also puzzles him and he makes an exception for her as an extraordinary woman with little in common with others of her sex. This is evident in what he writes about love in the Middle Ages. "In those days people loved each other for their lives, without the conveniences of the divorce court and the psychiatrist. They had a God in heaven and a goddess on earth - and, since people who devote themselves to goddesses must exercise some caution about the ones to whom they are devoted, they neither chose them by the passing standards of the flesh alone, nor abandoned it lightly when the bruckle thing began to fail." It never occurs to White that a lover may be female as well as male. The lover devotes himself to a goddess, the goddess to being beloved. His romanticism remains stubbornly phallocentric.
I would hope that modern feminist readers would have greater compassion for the character of Guinevere. Her thorniness, her moral courage, her refusal to give up what she wanted most, the sad fact of her infertility, her passionate love, and her unflinching tussles with duty - these qualities should endear her to feminists. But perhaps the fact that she is so relatable makes her less desirable as a feminist heroine. She isn't an aspirational figure because her life ends in tragedy and the ruination of everything to which she, her husband, and her lover had devoted themselves. Even so, if we reject such a character on the basis of her failure, which of us would not equally deserve rejection?