My sister has a problem with lying both to her family and her friends. She's starting to become a little depressed because she's losing a few of her friends and now spends a lot of her time on sites like Habbo. I've tried to tell her that it's because she's lying. When she invites her friends to a party and intentionally leaves someone out, she'll make up some excuse if they ask why they weren't invited. Another catalyst in this is that my mother will encourage it while my father, at work during the day, will be absent for this.
I have tried consulting my mother about this but she won't take me seriously; she usually doesn't for any situation. My sister tells me to get a life. I don't want my sister's dishonesty to lead to serious consequences as she progresses in her teens. Is there anything I can do?