You call people aunts and sisters, but their feelings are really different. Aunt feels very respectful to her and feels that she is older than that generation. Alas, she can feel a feeling of being respected, and the called sister has a little respect.

You can directly reply that I am still young, and ask the little girl to respect me politely and call me sister. When being called aunt by a 20-year-old girl, she showed a very realistic attitude towards her actual age.