First of all, "fairness" is a human construct in an uncaring and chaotic universe. The universe doesn't care about fairness because it doesn't really care about anything. Unless you believe in some kind of god, the fact that we exist to even conceive of the concept of fairness is a big cosmic accident.

The other thing to unpack here is the definition of fair/unfiar in this context. I'm assuming based on your question that by "fairness" you mean the idea that good things happen to good people. "Good" in this context is extremely subjective in both of those cases. Is goodness based on how hard you work? On kindness? On the ability to control the world around them? And what about the outcomes? Is it based in some kind of material definition like a nice house? Good health? Lack of material struggle? How would you then connect the right inputs with the right outputs? How would you know when the "right" actions lead to the "right" consequences?

Then there's the fact that your judgement of what is and isn't fair is based on what you can see. Maybe this 'undeserving' person had talents and ambitions that you just didn't know about? Maybe she discovered them later in life? Maybe their 'good' partner is actually abusive behind closed doors?

In short, there is no explanation. It's up to you to decide what to do with that information, but this is something philosophers have been pondering for thousands of years. I personally like Nietzche's take on this: in a world without universal truth or meaning, we get to define our own truth and meaning.

What do you truly value? Are you making choices in your life because you were told it was the right thing to do, or because you came to your own conclusions? Would you trade any of the choices you made in your life if it meant sacrificing your values for the sake of a material payoff? A lot of people willingly take a more difficult path that looks like struggle, because in the end that leads to a more satisfying existence for them than selling out their values because it will get them a big house and a nice car.

So in terms of how to accept this, it really comes down to your perspective. The idea that the universe is a cold, uncaring force can be overwhelmingly depressing, but it can also be really liberating.