Final answer:
The best way to assist the customer is by considering her skin tone, undertone, and personal style. Cool undertones can be complemented by red lipsticks with blue undertones, such as berry-red or cherry-red shades. Offer swatching and testers to help the customer find the perfect shade.
Step-by-step explanation:
The BEST way to assist the customer in finding the right shade of red lipstick is by considering her skin tone, undertone, and personal style. Since the customer has a pretty neck and pearl and pink whiteness of skin, it indicates that she has a cool undertone. Therefore, she should look for red lipsticks with blue undertones, such as berry-red or cherry-red shades. These shades complement cool undertones and can make her look flattering.
It is important to consider the finish of the lipstick as well. Satin or gloss finishes can be more forgiving and easier to wear for beginners. Additionally, the saleswoman can offer to swatch different shades on the customer's arm or provide lip product testers to help her visualize how they would look on her lips.
Overall, the key is to experiment with different shades, undertones, finishes, and to consider the customer's individual preferences to find the perfect red lipstick that complements her skin and makes her feel confident.