PT3. She has a complex on her nipple, and tries to apply a cream that makes her pink, but she is sensitive

My stepsister, who is concerned about the color of her nipples, buys a cream to make them pink and tries to apply it, but she can't apply it properly because she feels so much that she leaks out whenever her fingers touch her nipples... After struggling with this, she asked me, herstepbrother, to apply it! I reluctantly agreed to apply the cream to my stepsister's nipples, but...