I think the question here is whether the amplitudes and probabilities in the wave function are proper to the observer or whether they are proper to the system. In other words, can different observers "perceive" a different wave function for the same system.
Well, that depends on your interpretation of quantum mechanics. In the classical, "Copenhagen" interpretation of quantum mechanics, the wave function actually collapses when observed by some kind of intelligent being. All other beings in the universe will then see that the state has collapsed to the new state. Although this would be a non-local effect, it cannot be used to transfer information, and is, for all practical purposes, a self-consistent definition of quantum-mechanics. The down side is that it is not very elegant, and that there is no clear-cut definition of what kind of "intelligent being" is required to collapse a wave function.
However, in "many worlds" quantum mechanics, the wave function becomes entangled with the observer and only tells you about correlations between what the observer sees and what "collapsed state" the system is in. Since the observer only feels like they are seeing one thing, the wave function in this case will be subjective in the sense that the observer is in a superposition of many different, approximately orthogonal states, each associated with a different, collapsed, "Copenhagen wave function". On the other, hand, in each of these "branches" of the total wave function, the wave function of the system will appear to be objective because every other observer in the universe will also be in the same branch of the wave function relative to the observer.
A confusing way to say this is that the system is in an objective state relative to the universe, but the entire universe will itself be in a subjective state relative to the observer. The downside to this is that we have to believe in zillions of "copies" of ourselves, with no objective reality, only a wave of many simultaneous realities. Also not particularly aesthetic.
Those, and their variations, are pretty much the only choices in the market. Maybe some day we'll have a better understanding of quantum mechanics that is both elegant and corresponds to experience.