bro wtf goin on and why does ms.girl HAVE to sing ?

Lol apparently she has too much pent up mana and the only way she can release it is through singing....but tl;dr wattpad protagonists have to be good at something right?

yes, to add to what shiiro said, if she doesn't sing for a long period of time she could basically die. this happened before; she couldn't breathe.