[LlamaLlamaDuck]

Hey Miki! I love your name! Welcome to TeenHelp!

It sounds like a really tough situation you're in since you're torn between your brother's happiness and the wellbeing of yourself and your other siblings. Is there any other family you might be able to speak to about this? If not, maybe you could speak to your brother's girlfriend while he's there. You could all sit down together and point out that you think you got off on the wrong foot but you're willing to start over and be friends?
It might take time, but if this girl really is bad, then eventually your brother will see for himself. If she does anything to physically harm you or your siblings then tell your brother, show him, and call the police. Your home needs to be a safe place for you and if she's threatening your safety then she needs to go.
PM me if you want to talk about anything anytime.

Take care,
Louise.