So, everything happens for a purpose. That's the whole point of the movie.
So she HAD to be hit with a car so she could tell her husband to tell his brother to swing away when being invaded by aliens whose only weakness is water (of which there is a considerable amount in the atmosphere.) Anyone else have a problem with THAT being the grand plan? An otherwise meaningless death made meaningful because in her dying moments, the wife says "Swing away"? Of course, we're to infer that in those moments, she had some kind of premonition about the aliens weakness to water, and could only convey that is a silly, contrived manner that only makes sense due to a series of odd coincidences that come together masterfully like, you know, someone scripted it or something? Again, if the purpose of her death, or even the value generated is that her family is protected against the aliens, why doesn't the grand planner just have her say, "So here's the rub, you *****es are gonna be invaded by aliens, whose only weakness is water, so invest in super soakers." Everything would still be connected.
Obviously, the plotholes are enormous, but even the message is retarded. Everything is connected? Everything happens for a purpose? C'mon son, even if that IS the message you want to send, I would think a slightly less nihilistic vessel would be a more appropriate means by which to deliver it.