Frosbitten Crossing - Action: During a conflict at this province, choose a participating character – discard each attachment on that character.

Finger of Jade - Interrupt: When the effects of a card ability that targets attached character would initiate, sacrifice this attachment – cancel those effects.

Does "choose" from FC count as targeting? If so, would FoJ negate?

Yes, you could discard finger of Jade to prevent the Frostbitten Crossing.

Finger of Jade can prevent if you choose during the area before the dash as part of the cost.