At the start of the play we see Desdemona as a strong, outspoken and behaves in a way that is outrageous in her society. She has fallen in love with a man of a different race, country, and color; and she is so determined to marry him despite what she knows would be her father's opposition that she conceals her intentions and weds without her father's consent. Before Othello came Desdemona was described as perfect by Brabantio and she was sweet, modest and compliant, just like women of her status were meant to be.
When Othello comes, at first Desdemona is frightened of him but the things she fears in him is what makes her attracted to him like his race and warrior status. He excited her and represents all the possibilities she has missed out on in life. When he talks about the things he has done she live through his adventures. She believes that by merging in marriage with him she will gain his exotic past and share his adventurous future. The marriage provides her for an escape from her normal everyday life and enters the world of her dreams. Therefore she must seize the opportunity, this is why Desdemona speaks so speaks to the senate and rebels against her father. While she is fighting for her marriage, she suppresses her feelings of guilt; but they contribute later, I think, to her inability to defend herself against her husband's unjust accusations. Despite her boldness Desdemona has a self-effacing nature.
Desdemona’s fierceness with Othello on Cassio’s behalf isn’t the same as her rebelliousness she showed earlier but it is the typical self-effacing project of fighting for someone else. Iago understands Desdemona and knows that her compliant behaviour is compulsive and once