Actually no. Luna is the Princess of the Night. The Dreamscape is her domain. Luna simply allows other ponies to explore the realm in their sleep and protect them from the native creatures that live in this realm.
When ponies dream. Luna isn't the only thing that can see the dream in question . Her own creation, the Tanibus, is an example of such a creature and even ponies themselves can create their own monsters in this realm, their fears manifesting as shadows or nightmares.
Luna will only appear to a pony in distress. just as a fearful pony might attract a nightmare, Luna in turn will pursue it into the effected dream. Luna also uses dreams as a method of granting an audience. In humans, dreams are your mind processing the days events and planning ahead. In ponies, Luna can give them advice on how to overcome their fears and sleep peacefully.
Also, Luna is 1000 years old. She has probably seen dreams worse than anything you can cook up... yes, i'm talking to you, person who is reading this comment.