SiD is one validated detector design for the International Linear Collider (ILC) with strengths in particle flow calorimetery. The silicon — tungsten electromagnetic calorimeter (ECal) greatly contributes to this. Layers of highly granular (13 mm2 pixels) silicon detectors embedded in thin gaps (∼ 1 mm) between tungsten alloy plates give the SiD ECal the ability to separate electromagnetic showers in a crowded environment. A nine-layer prototype (5.8 X0) was built and tested in a 12.1 GeV electron beam at SLAC National Accelerator Laboratory. This data was simulated with a Geant4 model. Particular attention was given to the separation of nearby incident electrons, which demonstrated a high (98.5%) separation efficiency for two electrons at least 1 cm from each other. In the future, this beam test study will be compared to a full SiD detector simulation.