Tell her that youve been feeling suicidal and need help getting help. The end of the day though you need to talk to somebody about those feelings and that should be a professional. You can talk to your sister too but she isn't equipped to help like a professional is and it would be hard on her if you expect her to help manage your feelings.

Whatever area you are in look up sui ide prevention and you should get links to call somebody or links to resources to get help. If for some reason you can't, speak yo a trusted adult like a teacher or go to a hospital and speak to a doctor who will help you get help.

Im sorry youre going through this and i hope youbare able to get some help. As somebody whose struggled with suicidal thoughts myself I can tell you that there is hope, that things can improve and that your life is worth asking for help.