Asked to bond a crooked front tooth . dentist did x-ray first (inconclusive). so she tested it (had no feeling to cold). no decay, pain or trauma to tooth. does this always indicate a dead tooth?

No: Different patients have different pain thresholds. I have some dental patients who I can drill almost into the nerve and they feel nothing, while others jump and squawk at the slightest touch. The tests you mention are generally inconclusive and cannot be relied on solely to judge the vitality of a tooth.

Not always: Just because you're not sensitive to cold does not mean the tooth is non-vital. A pulp tester that places a small electrical stimulus will answer your question for sure.