I think what you mean is to go to another place and lay down, say on a dog bed, right? I would use a separate command for that - perhaps "Go to bed". That way, it's a different action than laying down beside you. "Go to bed" will mean go to the bed AND lay down. But you should only need to say "Go to bed: This is a different command than just lay down.
Set up your learning area by putting a dog bed, blanket, or towel about 6-10 feet away from you. With your dog beside you, on a leash if you want, say "Go to bed!" and then together go to the bed. The second she lies down on the bed, give her a treat. Say "Good girl, good go to bed!".
Then get up walk to the other side of the room again and repeat, "Go to bed." Together go to the bed and when you can get her to lay down, treat again. It will take many repetitions, but she'll start to figure out that going AND laying down on the bed will get her a reward.
Later, when you try to send her by herself, make sure that someone is waiting at the bed with a treat. Then you can phase out that person. Finally, she'll do it herself, and you will walk over to her while she is laying down and you will reward her.
I hope that's clear. Good luck and let us know how it's going.