[bookman156]

It's questionable whether the supposed motive force led her to do something or led to a situation arising. The sense of the sentence that I suppose is there is that she didn't intend to kill the person but it happened because of conditioning she was oblivious of until the situation arose and she'd ended up killing someone. She may of course still be oblivious of it, since it is the narrator speaking, not her. If that is the right reading, then her inability to tolerate ridicule didn't actually motivate her as such, but rather led to a situation arising. In other words, it didn't lead her to kill someone, rather it led to her killing someone. A subtle difference.