Hallo Frits,
not sure how variable it is.. In one south african spider group on facebook I follow these araneids are always entitled as "hairy field spider
Neoscona sp.", so I think that lady could belong to
Neoscona as well.
EDIT: Checking Bugguide and there are several specimen which are fitting your colour morph, uniformly brown with yellow shoulders:
http://bugguide.net/node/view/24094/Seems so that you have nailed it, especially as the coloured shoulders are mentioned in the description!
Check images for much more footages...
LG,
Jonathan