Only real, living humans can be diagnosed with Asperger's Syndrome, and only under DSM-IV (now superseded by DSM-V).
Bulma is a fictional character, and a poorly-written one, at that.
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The mere fact that science may not yet adequately explain an object, event, or experience does not mean the immediate explanation should automatically default to a conspiratorial, extraterrestrial, paranormal, or supernatural cause.