In your example, it seems that you did share an experience together.

It is great when you can share your dream with another person and then compare your shared experience.

You should plan with each other to meet in your dream reality and see if you can give a signal to each other, like a symbol that you and she are able to remember when you wake up.

If you are going to try this, you should keep your symbol a secret, and share this symbol with every person you meet in your dream reality.

Because your girlfriend may appear as a knight on a horse in your dream instead of as your girlfriend.

So flash that symbol or vision to everyone in your dream, and ask her to do the same.

This shared realty is actually quite common in our day-to-day existence but it operates in a slightly different manner.

We do this "sharing" whenever we intently focus on anything with great energy and emotion.

It could be an "excitement" based shared experience or a "fear" based shared experience.

Since we are all far more familiar with fear than excitement, it is easy to study your fears and see the connecting events where other participants share that same experience.

I am going to use the rest of this answer to expand on how fear attracts the experience of that fear.

Since the universe is balanced by opposing duality usually, the other participant in your "fear" is drawn into that same experience because of the need to fulfill the other side, or the duality counterpart of your fear.

So let us say that you are constantly afraid that someone is going to attack you from behind.

You will create an experience in consciousness where you are constantly "living" the experience of being attacked in your imagination and re-living that fear throughout the day.

By this action, an event in consciousness begins to exist, and you could say that an event in a parallel reality begins to exist.

Since reality balances on duality, your parallel event stays in balance by that fact that two participants are coming together to "participate" in this event.

You are only aware of your fear side of the event, but that event also needs the attacker's participation as well.

For the attacker, it is an excitement.

So as we "fear" about all kind of things happening to us we create various "events" that need the participation of others so that our fears can be fulfilled.

So all these parallel events stay in existence, waiting for the appropriate volunteer to show up to play the "other character" in our fear events in our imagination.

The other participant's automatically get attracted to us because they are also participating in the parallel version of the event.

Therefore, every time we are afraid of being attacked from behind we give permission to anyone who is interested in participating in the excitement of attacking us from behind.

The truth is even more sinister than that.

It is only when we engage our imagination in the "fear" of being attacked, that the very idea of attacking someone event "pops up" in the imagination of the attacker.

The idea "pops up" because it was created into existence in this "shared" space of consciousness by us, and it became available for others to "listen" to it.

So we can say that Fear = attraction, just like Joy = attraction.

Every time we fear of being attacked, we share that "dream" of being attacked automatically with the attacker who then becomes this "other person" who participates in our shared dream of fear.

Therefore, every time you are afraid of something we automatically share that dream with someone else, who becomes that person who fulfills our dream of fear.

That is what fear is.

It is your DESRIE to experience fear.

it could be i have read about a tribe somewhere that share dream all together. all the tribe is in the same dream. some time i dream of people when they think of me. before the revolt in egypt i was there scanning the mind of the people. so you see there is no limit. this morning in my dream i was talking to someone name paul saying to him that he should have walk in my foot step with faith like he was suppose to. and i do not know anny one name paul. but you see we are more linked that we know. experience and enjoy.

This may be possible, I have heard of influencing peoples' dreams. There was a great film called Dreamscape in it people enter into other peoples' dreams and change things, even kill people. You can watch the full movie here free with limited commercial interruptions.

Here is some research on dreams being influenced from outside forces.

I have discussed this question at length on my dreamtraining blog. The article is here:

Can two people dream together?