Wave function collapse is not relative to the observer. Either the wave function collapses, or it doesn't. The problem is that there is no clear definition of what a measurement is, or for that matter what a wave function collapse is. It is pretty clear that quantum effects like the linear combinations of states does not translate into the macroscopic world. The reason why, however, is unclear.
That is to say: The cat (or for that matter, physicist) dies, or doesn't die, irrespective of if you observe it or not. Schrödinger's Cat is a mind experiment used for reductio ad absurdum. It is not something that actually happens in the real world.