Natasha Bedingfield is very successful. And who cares if someone else likes Lady Gaga or Keshia better? Who you or anyone else SHOULD be listening to are singers that you like, not just singers other people like because you are afraid they might think you aren't cool or something.
At thirteen you should be deciding some things for yourself. You have to listen to parents and teachers of course, but usually this is the age where you can pick your own friends, your own clothes, your own hairstyles, your own hobbies, and certainly your own tastes in music. At least Natasha Bedingfield doesn't have the kind of songs or music that scare old people!