About Jess and Ivy. Actually more like Jess is Cindy, Ian and... Perry! Wait, don't throw tomatoes.
Although Jess was a possible guide for Ashley into the world of corruption and she had advices similar to Ivy, however, unlike the latter, she was still not a dark sociopath, weaving a network of intrigues that were not immediately clear. Ivy has clear goals and plans, and she achieves them in such anti-social ways. Jess was just a lost person who lost herself in glamor, fame and entertainment due to a conflict of interest with her parents. She had a creative spirit and creative passion, but she could not and no longer wanted to realize them because of this conflict. And also she had no real friends, only gigolos like Jack. And so friendship with Ash can help her get back to what she originally wanted, as she gets what she was deprived of.
In Ivy, there is nothing like that, she enjoys what she does, as it is completely her decision. She knows how to use her sexuality and depravity to her advantage. And she enjoys corrupting others like Lena and Holly. And she does this with specific goals, as another tool for her own promotion. When Jess pushes Ash onto her path, she does it without much malice, just out of inertia, as she lives like that herself.
This is the big difference between them.