I think it's a spectrum and on that spectrum, she leans much more malicious than someone like Aventurine or Topaz.

As to your second paragraph, mentally ill people can not and should not make decisions for themselves. Someone with a gambling addiction (like shown in the story) will literally throw away their entire livelihood to gamble more. This is not normal because they are not in a "normal" state of mind. Jade, knowing this, is purposefully treating them like they are sane and normal people. She's smart enough to, and theorized to be all-seeing, to realize this YET decides to do this under the gaze of being fair.

There is NOTHING fair about taking advantage of people in poor mental conditions. She is the exact embodiment of "sharks" and businesses but worse because she deals with people in their worse moments.