Racists come in all shapes, sizes and ethnic groups.
Not sure about this, but I've got a feeling that it started out personal for this woman. Like her husband or boyfriend left her for an Indian woman. It's just odd to have such pathological hatred of a particular ethnic group such that you have so little self-control in public. Most committed racist types keep their shit together most of the time, and when they attack, they attack in groups, because they're cowards.
She probably has depression issues, which explains the anger, and also issues with self-control and aggression.