Increasing racial diversity as a solution is a recommendation without empirical grounding. I am a white male and I work part time in ed tech. Our department is quite mixed - both my supervisor and the head of our department are black woman. However, there is little collegiality here.

And this matches the literature - the more ethnic/racial diversity in a community, the less civic engagement and trust (1). I'm not sure what the answer is, but the research suggests diversity is not a universal panacea. Like anything else, there are benefits and liabilities involved - and there are other considerations to take into account.

For example, I wonder if her co-workers had been more like her in other ways, such as matching her taste in video games, dress, attitude and so on - if her experience would have been different. In my department I suspect it's mostly these other things (work and personality styles especially) that are the reason for the lack of cohesion.

The best groups I've been a part of are those that mixed the right amount of same and different. We need to feel some commonality with others to form bonds, but we also need enough differences to challenge and stimulate us. Effective hiring practices require attention to both, else company and employee will suffer.

(1) http://www.boston.com/news/globe/ideas/articles/2007/08/05/t...

*Edited to expand on the point/add clarity.