Does anyone know why Selena is leaving Wizards of Waverly Place?

i think its because all disney shows end at the forth season. ITs not that selena wants to leave just she has to leave because of that

WHAAAT?????!!!!NO U CAN'T DO THIS SELENA!!!
NOOOOO!!!

I THINK IT IS BECUASE DISNEY ITS GOING TO DO ANOTHER SERIES AND DISNEY HAS TO LET OTHERS STARS SHINE

well she actually isnt because i chat with her all the time and she says she might abnd might not so there.