Reylo

The Vision

This is the scene from the movie:

The first time Rey is shown having the Force was on Takodana, when the lightsaber called her in Maz's palace. It was also the first time we see Rey and Kylo Ren together.
When Rey touches the lightsaber, she saw the memory that had haunted her most of her life, the day that her parents abandoned her.

The Force was showing the pain that she was holding in her heart.
But she also saw the most painful day of Ben's life, the pain that he was holding in his heart. The day that he turned to the Dark Side.

After watching the Last Jedi, we see that this was the night when Luke thought that there was no hope for Ben, so he tried to kill him in his sleep. Then he realized his mistake but it was to late.

The two visions she had of the past was the worst day of her life and the worst day of Ben's life. The days when their family who should have taken care of them no matter what, gave up on them.