All of a sudden Saya has decided that it is time to become highly annoying. She does not let anybody sit in the couch except me. When somebody sits in the couch she will try to play with them and start nipping their hand. The only one who is able to sit there is me, she knows not to try that with me because I dont let her get away with it. Once she sees is not going her way she will start barking like a maniac. She also barks when we are eating but only does it sometimes. And her last annoying habit that I'm trying to get rid of is her nipping her big teeths are in and now she loves to nip more than ever. I hate it when she tries to do so, if I'm ever petting her after a few seconds she will try to nip at me. When I'm sleeping sometimes she will try to wake me up by nipping at me. She rarely gets her ay with me but it is still highly annoying.

Any advice?

The barking when eating, I'd put her in another room, or even in her crate with a chew while you are eating.

Every time she nips hands I'd get the person to get up and move away. Play stops when she behaves in an undesirable way.
With the nipping while on the couch, I'd put her in time out every time she does this.

Sadly your 6month old is now in the "Teenager" stage of puppy hood, pushing the limits and seeing what she can get away with, stay strong and stern and I am sure she will get the point. When Thunder acts ups or misbehaves in the house he gets put outside(He hates being outside alone). He gets the point that is he wants to be in he has to be good.