It's probably because she is a noble. It's a matter of class more than anything else, stupid, but yeah that's how it can be sometimes in societies with strict class brackets.
So she wouldn't really know folk songs because she would have to be taught by a commoner.
I think it has to do with the fact that those folk songs are about revolution and are “pagan” I think? And that the rich and wealthy sing the temple songs; as in the old days royalty as well as nobles believed that God gave them power, wealth, and majesty over the lesser and poor.
So the fact that the wealthy class sing temple songs while the poor and common people sing their own folk songs is a distinct evidence of ones upbringing.
But also that the specific songs she’s singing are from the future during the war or revolt and the songs are very... anti - noble or royalty.
So she could be in danger for singing such songs...
... I think..? ╮(￣▽￣)╭
I still don´t really get why it is taboo to sing folk songs or sad songs.
The common people seem to sing them anyway and don´t fear for their lives.
But she is only allowed to sing temple songs???
Can someone explain the reasoning behind this, please.