台Taivo A Taiwan Mandarin dictionary

小姐姐

xiǎojiějie

ㄒㄧㄠˇ ㄐㄧㄝˇ ˙ㄐㄧㄝ

1little girl who is older than another young child (e.g. her playmate)
2(neologism c. 2017) (slang) young lady (amiable form of address for a young woman of about one's own age or a little older)

Keep 小姐姐 and it comes back until you know it.