She's not the first actress who shifted to singing. Look at Selena Gomez.

Well, the thing about "brands" is that every artist needs one nowadays to stand out. You can't just be a good singer or songwriter; you have to look the part or act the part, otherwise you'll end up as one of the crowd. But it still has everything to do with your voice being recognizable and/or your music being unique and/or your name having some backbone. Plus, it also helps to have a fan base behind you; if nobody believes in your music, how do you expect to get noticed by a record label in the first place!?