Or is it this reason:
From the lay of Sir Lanval:

Now it chanced, the same year, about the feast of St. John, a company of knights came, for their solace, to an orchard, beneath that tower where dwelt the Queen. Together with these lords went Gawain and his cousin, Yvain the fair. Then said Gawain, that goodly knight, beloved and dear to all,

"Lords, we do wrong to disport ourselves in this pleasaunce without our comrade Launfal. It is not well to slight a prince as brave as he is courteous, and of a lineage prouder than our own."

Then certain of the lords returned to the city, and finding Launfal within his hostel, entreated him to take his pastime with them in that fair meadow. The Queen looked out from a window in her tower, she and three ladies of her fellowship. They saw the lords at their pleasure, and Launfal also, whom well they knew. So the Queen chose of her Court thirty damsels—the sweetest of face and most dainty of fashion—and commanded that they should descend with her to take their delight in the garden. When the knights beheld this gay company of ladies come down the steps of the perron, they rejoiced beyond measure. They hastened before to lead them by the hand, and said such words in their ear as were seemly and pleasant to be spoken. Amongst these merry and courteous lords hasted not Sir Launfal. He drew apart from the throng, for with him time went heavily, till he might have clasp and greeting of his friend. The ladies of the Queen's fellowship seemed but kitchen wenches to his sight, in comparison with the loveliness of the maiden. When the Queen marked Launfal go aside, she went his way, and seating herself upon the herb, called the knight before her. Then she opened out her heart.

"Launfal, I have honoured you for long as a worthy knight, and have praised and cherished you very dearly. You may receive a queen's whole love, if such be your care. Be content: he to whom my heart is given, has small reason to complain him of the alms."

"Lady," answered the knight, "grant me leave to go, for this grace is not for me. I am the King's man, and dare not break my troth. Not for the highest lady in the world, not even for her love, will I set this reproach upon my lord."

When the Queen heard this, she was full of wrath, and spoke many hot and bitter words.

"Launfal," she cried, "well I know that you think little of woman and her love. There are sins more black that a man may have upon his soul. Traitor you are, and false. Right evil counsel gave they to my lord, who prayed him to suffer you about his person. You remain only for his harm and loss."
https://en.m.wikisource.org/wiki/Lays_of_Marie_de_France/The_Lay_of_Sir_Launfal