Why is Suzuha pre-destined to die in 2000? Suzuha inevitably dies in 2000 after traveling back to 1975 to obtain the IBN.

It doesn't create any paradoxes, so there is no reason why she can't live to 2010 as long as Suzuha doesn't interact with her other self and the lab members until "August 9th, 2010" (the date she departs for 1975). Okabe has already demonstrated that you can co-exist with your other self.

Is her death just another convergence of the worldlines? If so, why? What significance does Suzu's death have on the worldline that the "universe" demands that she die at that point in time?
From the wikia:


  However, she dies cause of an illness due to her time travelling in 2000 at the age of 43. 


It just seems like the time traveling had a physical toll on her body which caused her death.