Reylo

The Connection

I have seen a lot of people asking how Rey went into his mind when she didn't know anything about the Force.

This is my theory:
Unlike anyone else Kylo has looked into the mind of, he didn't just want to find the map, he wanted to learn more about her. Because he wanted to learn more about her his mind was open to her. She simply went through the open door. He unknowingly welcomed her into his mind.
I think that because he saw so much of himself in her, he unknowingly shared things about himself with her.
According to Star Wars resources Rey learned about the Force by seeing Kylo Ren's training. He later offered to teach her. He may have sensed the Force within her and had a desire to teach her how to use it from the beginning. Because of that desire he might have subconsciously showed her what he knew.
If Rey saw his training it would explain a lot of things. How she was so strong with the Force so quickly, and how she was able to beat Kylo Ren so easily. If she saw his training she would know his fighting patterns and be able to counter act them.
But I have a farther theory about how Rey was able to get into his mind.
I think that Rey and Ben have been connected through the Force their whole lives.

There are several things that point to this.
One
When Kylo Ren learnt that FN-2187 and the droid were helped by a girl he was surprised. He asked "what girl?" As if he knew of a girl.
I think he had had visions of her in the past. I think he saw her in the past, her past as a child, (which may have even been the present at the time when he saw it.) But I also believe that he saw parts of her future.
These are the parts of her future I believe he saw :
I believe he saw her wield the Skywalker lightsaber.