Why do I keep having nightmares about this ?

Maybe you keep having the dreams because you’re scared something will happen to her, and you think, “I don’t want to dream about this” when you’re going to bed. Then you end up worrying about it and dreaming about it again. I suggest you think about something else during bedtime. Not that that’s necessarily an easy thing to do. You could also try to lucid dream, I guess.
Of course, if you never think about this during the day or during bedtime, it just pops up in your dreams, I don’t know how to help besides lucid dreaming.

Just accept your dreams and don’t try to fight them off. If you’re fearful of them and keep trying to “avoid” dreaming of them, then you’ll keep dreaming them. It’s like that awful song that keeps playing in your head over and over, and you want it to go away but it doesn’t, until you start humming it out loud and accepting it. What you’re experiencing is pretty normal.

We usually dream fearful things about those people or objects we love or care about. In real life, we don’t want to think about those things happening to them, so we repress them. As a result, it comes out in our dreams for us to confront. Once we accept them, they usually disappear.

I think you are really inspired by the singer. Also, it would probably just really suck if you missed out on her. To me, you are just really anxious and excited to see them. Let go of all your worries and just enjoy it when the time comes.

to have a dream (or a nightmare) about the same subject many times means that you keep thinking and worrying about the same thing (which is in your case “the band”). You just need to relax more and stop worrying yourself and hopefully, you will stop seeing those nightmares.
It’s just as @MRSHINYSHOES said, you keep dreaming about them because you care about them. Just stop worrying and “everything will be alright”.

Your husband is having an affair. Your dreams are reflecting this through this band. You are the “lead singer”...and will be replaced if the affair doesn’t end.

@SpatzieLover way to think