Even though I do t want to ser her die, as if was stated above this is a war. It is kind of unrealistic if only the bad guys die. Plus Naruto can't become Hokage while Tsunade still holds that title. Her death makes way for Naruto to become Hokage, and gives Sakura a reason to get a power up as the new Slug Sage. So it kind of looks like she needs to die for plot purposes.