Final answer:
To close the sale, affirm the customer's choice of the band that complements the watch, and offer to adjust it to fit her wrist, thus guiding her towards the purchase.
Step-by-step explanation:
In order to close the sale with the customer who tries on a watch and has expressed interest in a particular band style, a suitable approach would be to affirm her choice and guide her towards the purchase. For example, you could say, "That band really complements the watch and looks fantastic on you. Shall I go ahead and adjust it to fit your wrist perfectly?" This reinforces the customer's good taste, addresses her request, and moves towards finalizing the sale in a friendly and professional manner.