For Dayoung, her new solo EP “What’s a girl to do” is more than just a comeback. It’s shaped by the music style she practiced with during her trainee years and the kind of artist she wants to become. Set for release on Tuesday, Dayoung’s second EP, “What’s a girl to do,” marks a stylistic shift from her previous EP “Gonna love me, right?” drawing more heavily on early-2000s R&B and dance-pop influences. “I have a lot of nostalgia for that era,” said Dayoung during a round table interview in sout