Backstory:

My little sister just turned 18. She's a lightskin to brownskin black girl and In recent years, her boobs grew to be really big and her booty is jiggle and pretty big too, but she still has a small waist and isn't fat. Her lips are really plump and always have lipstick and her face is really clear. She has one of those cute but seductive looks (no l'm not sending pics). It makes me infuriated how she dresses in public. She wears crop tops with deep necks so her cleavage is always bouncing around where you think she'll have a nip slip any second.

She always wears either insanely short and tight jean shorts or insanely short and tight Nike pros that let her under cheek hang out and make her thigh meat spill over because they're so tight. They make her thigh gap noticeable and you can always see the outline of her camel toe.

I started noticing guys staring at her in public or making comments about her body or what they'd do to her and she seems to not care that it would make her brother angry to be dressed so slutty in public.

She runs and jumps around either no care about her boobs bouncing or what anyone might see.

Problem:

I don't remember the first time I masterbated to her but it's never been just to her. The anger of seeing her be a slut and what guys may do to her somehow turns me on, but over the past year, it's gotten to the point where I can't cum unless I'm jerking off to a picture of her while imagining a man groping her or raping her. I cum to videos with cuckbro captions about a bully forcing me to watch him use her for hours. I cum to stories of other guys hearing or seeing their sisters have sex or deepthroat big cocks or get groped or raped because it makes me so angry and that anger turns me on. Idk what to do because she's always around guys wearing absolutely nothing. I've seen her bring guys in and out of her college apartment room. I can only imagine and cum gallons while crying about what's happening to her at a party or in her room.

I need help. Whether someone knows how to safely talk to her about stopping this, or honestly if someone wants to just make this worse and force my imagination to run even wilder. Idk what I need. I'm just a confused cuckbrother at this point.