Don't share this with anyone, but I potentially ruined my older sister's relationship.
Why would you do something like that?
I want her boyfriend for myself.
I get that you like her boyfriend but he's not your boyfriend, he's your sister's. Messing up their relationship is really petty and narcissistic of you. Your sister is going to hate you if she finds out what you did.
It's not like I'm hurting anyone physically.
Sometimes emotional hurt is worse than physical pain. Your behavior is destructive and lacking empathy. Put yourself in her place.