She was totally narcissistic in season one--using people and being a little self-righteous and ditzy about it. But the writers try to salvage her character by giving her some depth in season 2. They show bits of her family heritage; they show that in more obvious ways, she's very screwed up and why; and they make her the mouth-piece who stands up to one of the seasonal "bad guys."

Plus there is some Shane+Jenny bonding, and everyone gains coolness points once they've been friended by Shane.