How to comfort a girl ?

My sisters upset about this teenager who's on Instagram going around stalking and threatening rock bands. She's a huge Motley Crue fan she loves Vince yet she goes around bullying other bands and autistic people. My sister is autistic which is why it upsets her she blocked the girl a long time ago but her sister is posting everything she says on her story. First she said that Vince killed the Hanoi Rocks drummer she made fun of his death saying Vince shot him then she laughed like she had no sympathy for him Hanoi is my sister's favorite band so that upsets her she hates Vince with passion and Crue. Then she said it was the drummer's fault he wanted to get himself killed no one wants to do that. Then she started making group chats with rock stars such as Motley and Skid Row she got blocked by them. Then she went after Quiet Riot. My sister is worried she'll go after Hanoi and the Beatles. I don't know why she's doing this or what she's doing but she sounds like an evil little girl she's only 14. She told an autistic girl to slit her wrist who says that. She once told my sister that Gene Simmons once told suicidal people to kill themselves she blocked her after that because she is bipolar and suicidal at times. Sounds like all she cares about is Vince she said she wouldn't even like Crue if he wasn't in the band and death how can one 14 year old cause so much drama. My sister is really upset about all this she's 30 she doesn't even talk to teenagers on Instagram she just sees it on their stories. She's upset about the whole autistic thing. She was also making fun of Axl saying what a scum he was an she blocks anyone who supports him my sister loves every rock bands and supports every member except Crue.How can I comfort her ? Why are teenagers so mean these days especially online ? What happened to keeping conversations private instead of blasting them on social media ?