'Aunty' (also spelled 'auntie') in modern teen slang is often used as a friendly title for any older woman who feels like family — a friend's mother, a teacher, a neighbour — not literally a sibling of a parent. In South Asian, African, Caribbean and Filipino communities the broader use is the cultural norm. Among Gen Z online it can also be teasing: calling a woman 'aunty' may flag her behaviour or style as old-fashioned. Tone tells you which sense is meant; usually it is warm. It is not rude unless your child sneers when saying it.