Nina was diagnosed with Bipolar disorder and was medicated at various points in her life.
As a permanent side-effect of medications she developed a mild-to-severe case of tardive dyskinesia, which caused ticks in her face and mouth, and involuntary tongue movements. However, accounts from her close friends and family stated that if she was not medicated she could not manage her career and/or personal life.
I've always been curious about the relationship between creativity and mental health, even took a course in college called "Creativity and Madness" that explored the topic.
However, in Nina's case it's been my impression that her mental health negatively affected her art, rather than contributed to it. I think part of this is also the fact that many artists, while they excel at being creative, aren't great at managing their careers or the business side of art and entertainment, so her creative impulses might've been impeded by her struggle with managing her own career.
I think what Nina desperately needed was a manager that was passionate about Nina, looked out for Nina, and truly had Nina's best interests at heart. With the right manager, I believe she could have thrived.
Then again, I also know that Nina could be difficult to manage, so I'm not entirely sure the typical artist/manager relationship could have always endured her temperament.
She did have some very close companions that looked out for her (Roger Nupie and Gerrit de Bruin come to mind) but I don't think either of them were equipped to fully manage her career.