I love dreams for many reasons. One of which is that they are able, within an instant, to bring us back to any moment, any time - and we can, quite literally, relieve those moments.

Sometimes, dreams can mean that the other person is thinking of us. Other times, it could mean that they are simply on your mind.

Other times it could be precognitive.

But since you both moved on, in this case, it could just be a 'hello', as it seems as if the two of you are still connected.