Help? My sister is terrible at singing?

start screaming in the middle of the night

To get your sister to stop singing around you, I would suggest engaging in some underground psychological warfare with your sister.

Here's my advice:

The next time your sister starts singing near you, just lean in close and politely whisper into her ear "I've got a confession to make, Sis..... all of the beautiful singing that you've been doing lately is getting me REALLY excited. Yeah, I've kinda developed a sister fetish, and you've become my fantasy GF. No kidding. I've been watching Game Of Thrones, and reading lots of anime about brothers and sisters who are BF and GF. Siblings-as-lovers are SO HOT!!!! Please don't stop with the singing, because I absolutely LOVE everything about you, your voice, and your body.... plus, I also think that you're SUPER CUTE!!!!"

But before whispering to your sister about your fetish, review a few links so you'll have a basic understanding about what it means to have a sibling fetish in case your sister exclaims "WTF?!??!?!" and demands an explanation - https://answers.yahoo.com/question/index?qid=20151... .

Your sister will be repulsed that you find her attractive, and stop with the weird behaviors.

In the unlikely event that your sister gets excited and actually thinks that you're serious and she wants to become your taboo GF, then you'll have to confess to her that you were trying a psychological warfare experiment on her, and it didn't work out the way you thought it would because she turned out to be much stupider than you could have possibly imagined.

This sort of thing happens often, don't worry. My expert advice:

The best thing to do is to pour gasoline in your backyard in the shape of the words, "aliens please come abduct my sister", then set fire to it and sacrifise a few baby goats to the gods. She'll be gone by morning.

Trust me, it worked for me.

why don't you move out.