His LUNCH cost his mom her life?

Rating: 10/10 (11 September 2013)

At the beginning of the movie he tells his mom congrats on her 25th 25th birthday. Then she gives him 30 minutes for a good lunch. Later she dies because her time runs out... My question is to you all is this did she die because if she hadn't given him those 30 minutes she would have made it to him for the time? I got confused.
Did she lose that time somewhere else?
Or did she actually die because she gave him those minutes and thats why he tries to change everything?
did I miss something?
Or am I right that if she didn't give him the 30 minutes for lunch she would have made it to him and been saved with all the time he had acquired?