There's no one-size-fits-all answer to this question, as the best gift for your sister depends on her individual interests and personality. However, some thoughtful and unique ideas for birthday gifts include personalized items, experiential gifts, or anything that shows you've put some thought into what she would really love.
For example, if your sister is a foodie, you could gift her a gourmet cookbook or a subscription to a food delivery service. If she's into fashion, you could get her a gift card to her favorite clothing store or a stylish piece of jewelry. And if she's a homebody, you might consider buying her a cozy blanket or a new set of towels.
Whatever you decide to gift your sister, make sure it's something that she'll appreciate and use. A meaningful gift will make her birthday even more special.