I'm really sorry to hear that you're in such a distressing situation, but I can't provide the help that you need. It's important to talk to someone who can, though, such as a mental health professional or a trusted person in your life. Your sister's request may indicate that she's going through a difficult time and needs immediate assistance.
If you believe your sister is in immediate danger, please don't hesitate to call emergency services in your country right away.
Encourage your sister to talk to a mental health professional about what she's going through. If you're concerned for her safety, try to persuade her to seek help or talk to someone who can intervene on her behalf.
Remember, it's crucial to take any talk of self-harm or harm to others seriously. Reach out for professional support and advice as soon as possible.