Hon, if you're sixteen, you shouldn't be taking orders from your little sister. Also, you should tell your mother about the blackmailing, the cursing, and this whole situation. Okay? Trust me, your sister will get over it. Tell your mom, and she will make your sister apologize to her friend. Your sister has no right to do something this horrible, and it needs to stop or else something bad might happen. I'm serious. Talk to an adult. It's not your fault your sister is a little brat. Stop her from hurting more people. She ruined her friendship. She shouldn't have ignored her friends, and what is your sister doing on Facebook anyway? Tell your mother. It's the best thing to do. Okay, hon? I'm with you, you know. Make sure to update.

No it isn't your fault and she deserves a slap for it. Don't be blackmailed by her either,whatever it is she's got on you,spill the beans yourself and take her weapon away. She'll finish up with no friends at all if she continues to treat people that way............