How do Harper Lee and John Steinbeck present Mayella and Curley's wife as both victims and as aggressors?
This is a nuanced question. You are correct in saying that the women are portrayed as both aggressors and victims.
For example, Mayella is a victim of her situation. Bob Ewell is a drunk, a poor father, and a menace to society. Mayella inherited her situation, and it is tragic. However, when she is on the stand, she lies. She allows an innocent man to go to jail and possibly die. She ruins another man's life. So, she is an aggressor. Here is what Atticus says:
“I say guilt, gentlemen, because it was guilt that motivated her. She has committed no crime, she has merely broken a rigid and time-honored code of our society, a code so severe that whoever breaks it is hounded from our midst as unfit to live with. She is the victim of cruel poverty and ignorance, but I cannot pity her: she is white. She knew full well the enormity of her offense, but because her desires were stronger than the code she was breaking, she persisted in breaking it. She persisted, and her subsequent reaction is something that all of us have known at one time or another. She did something every child has done—she tried to put the evidence of her offense away from her. But in this case she was no child hiding stolen contraband: she struck out at her victim—of necessity she must put him away from her—he must be removed from her presence, from this world. She must destroy the evidence of her offense.
As for Curly's wife, she is a victim of a male dominated society. There is no evidence that she has any female companionship. Moreover, she has a deadbeat husband - Curly. She says on several occasions that she could of had a better life. That might be true. That said she is flirtatious with the men, even though she knows well that they could get in trouble. At this point she is only thinking of herself.