Adding an お in front and a さん behind miss makes for a very respectful way of addressing ayoung lady. It can also be used to refer to somebody’s daughter in a polite manner.
Note that older generations tend to use this word to directly address a young woman. But be careful when doing this yourself, as it might come across as overly formal!
The reading of 嬢 is the same as the one you learned for the kanji, meaning you should already know it!
Isn’t the manager’s daughter a wannabe singer?