It is impossible to label Tess as an entirely passive or assertive character as she frequently fluctuates from one to the other. She is constantly battling against her oppression as a female and trying to understand new experiences which are the major causes of her inconsistency.
She has a sense of duty regarding family and often acclaims the role responsible head of the household when the father is anything but and the mother is bawdy, taking every opportunity to exploit Tess. Tess is passive regarding accepting her mothers wish to send her away to the D'Urbervilles with the prospect of marrying her off to Alec and even letting her know her intentions. Her parents make poor role models, no doubt contributing to Tess' unstable character. John Durbeyfield, her father has little influence over Tess and only fills her with sorrow and disappointment. She is the key to her father's design to regain the family fortune, for he intends to marry her off to a gentleman who will provide for her and themselves; however, Tess has no say in her father's plans.
It was no secret that other families have amounted to little despite their former high esteem when attempting feats such as this before but Tess wasn't to know this. Joan Durbeyfield, Tess' mother is aware that Alec is likely to make a pass at her daughter within the first third of the novel and pressures Tess to accept. Though Tess understands the families impending poverty she still dreams of personal happiness, and when her dream is compromised her assertive aspects become evident. This can be seen when Tess' hat is blown off whilst in the carriage and uses the opportunity to break away from Alec's torment,
'The hat was in place and tied, but Tess had not stepped forward. "No, sir," she said, revealing the red and ivory of her mouth in defiant triumph; 'not again, if I know it!"
"What - you won't get up beside me?"
"No; I shall walk"
"Tis five or six miles yet to Trantridge."
"I don't care if 'tis dozens. Besides, the cart is behind."'
This stubbornness was one of Tess' most useful attributes around Alec; she wouldn't let him have his way with her for as long as she kept up her guard. It is uncertain however, where this quality of hers derived from as it certainly wasn't from her elders. Her father offers no guidance, support or any form of encouragement to help his daughter survive in a world with laws suited to men. She is subject to the wishes of her family and afflicted by their sense of irresponsibility.
Perhaps if she wasn't so fatalistic then she would be more assertive, although to some extent she is a victim of circumstance. It is primarily the death of the horse, Prince, the Durbeyfield's main source of livelihood that commences the circumstances that envelope Tess. Tess views herself as the cause of her family's economic downfall,
'Nobody blamed Tess as she blamed herself... she regarded herself in the light of a murderess.'
This pressure of being responsible for the family's loss of income makes it hard if not impossible for a girl as guilt prone as Tess not to do as her parents tell her.
Ultimately Tess is at her most assertive when she realises that she has no other choice, whether it is for her own well being or due to a lack of action from others. She has had no stable role models to guide her or inform her as to how to act in the world thus making every decision she makes a lesson in life. It is these unfortunate circumstances that lead to her to her erratic methods of coping with situations.