[Isabella] was a woman of conscience; when she found that two of her sisters-in-law were guilty of adultery with two French knights, she had no hesitation in reporting them to her father. It is not difficult to find instances of her clemency: ....
I. Mortimer, The perfect king: the life of Edward III (2006), 25
This feels like weak evidence for her conscious and especially her clemency. The knights in question were executed and Isabella's motives are ambiguous.