Wait a second, why does everyone assume Hanners is rich?
Sure, her parents are and she will be once she inherits her parents' company shares, but we know nothing about how much her parents support her financially right now. I am sure that she gets some support because you can't afford a nice appartment like hers on a part-time coffee shop job and probably her therapy and medication is quite expensive, too, but she might still want or need to earn something herself. Remember that before her coffee shop job, she had a business counting things for money.
Also, just being a rich kid* and expecting your parents to pay for everything you do is not a fulfilling life for some people. I think it's perfectly natural to want to have your own job and gain a little independence by earning your own money.
Edit: * Forgot the point that Hanners is not actually a kid anymore. She's at least 23 (citation needed). As an adult, you generally need to provide for yourself. It's nice of your parents to support you if they can and you need it, but you can't sit around and expect it.