I loved this movie, but one thing that did not ring true was When Sandra was trying to be "white", her wild messy hair made her stand out. I suspect this is the actress's style, not that of the real person. Such a person would likely have straightened hair, or at the least a neat Afro.
shareperhaps as 'white' people they didn't know what to do with her hair - to ask the staff would be like admitting that she was 'coloured'
shareThe few childhood photographs that I have seen of Sandra Laing would suggest that they did not straighten her hair, though she did wear it short and sometimes flattened against her head. What's interesting is that it ~does~ seem to be short, and growing it very long (if she even could have done that, as some people can't) would probably have minimized the curling effect, making the hair appear a bit straighter and more wavy. Longer hair might also have helped to discourage tanning of certain parts of Sandra's face, shoulders, and neck, and depending on what clothing she was wearing and how she wore her hair, possibly even her chest and/or back.
If anything, Sandra's hair appears to have been done in a hairstyle which made her presumably dark-skinned African ancestry all the more obvious. There were ways that they might have tried to work around this, but I'm not sure if the parents knew about them or if they would even have worked for or been acceptable to Sandra/her family.