Controlling what you dream about(?)

I had a friend of 16 years and more who is in love with a singer in a popular 90s band(obsessed) and it's no way reciprocated. She says he loves her in another dimension and she controls her dreams to speak to him. I use to have to listen to her talk about her fantasy conversations with him until i could no longer take talking about some delusion. She is no longer the fun person I use to know... just lost in a delusion and I and all her family/friends tried to make her snap out of it.. but no one is more important then the delusion :-(

Is there another reason why one would want to lucid dream other then to create another reality that doesn't exist?