Greatly depends on...
-What kind of person are they?
-What kind of "life or death" is it?
-Was it brought about by them? If so, intentionally knowing the risk?
-Can I actually do anything to change the situation?
-Who would be affected by the loss of?
A lot of factors, but I currently don't have "friends" in my life I'm willing to go and "die for" (maybe one). Had more before but we went our separate ways after high school.
Though maybe I should rephrase it. I would never "lay down and die", but that I would seek out a path in which both of us live, at the risk of my own life.