Has This Idea Been Done Before?

I had this really great idea for a story a few months ago, and since then I've been busy planning it, and when I finally got most of it planned, I showed some people. Apparently it reminds them of other stories, mostly video games and TV shows.

This is the synopsis: "Liling was just a normal girl, until her father found an ancient Chinese artifact called the Dreamworld Necklace. It allows it's wearer to travel to the dream world, where there are two other gems, which when combined with the necklace allow the wearer to control the dreamworld natives and allows them to come into the real world.

When Liling accidentally ties herself to the necklace, she's in a fight for her life, and the fate of her world, as well as the dreamworld, as she sets off the find the gems before her enemy finds them, so he can take over both worlds."

I showed a more detailed version to my former friend Matthew and he said it reminded him of Elder Scrolls: Oblivion. I've never played it, so I wouldn't know. I just brushed it off, but then I showed it to another friend of mine and he said it'd been done before. He said he saw an anime show on TV a while ago with a character that had a necklace that let him go into the dreamworld, and the show took place in space. He couldn't remember the name of the show, and I searched it but can't find it.

Does this sound like any other story you've heard? Cause I don't want to be sued for copyright infringement of anything because it's similar to some other show or book.