How to help someone who wont stop talking about what other people do.

I want to help my sister. Every day from the moment she wakes up, and it even keeps her up at night, she gets so bothered by what everyone and i mean everyone around her does. She has a pretty long commute which probably doesnt help, but espescialy when she drives to and from work or anywhere for that matter, she thinks people are on her tail, people are going too slow in front of her, or people are driving recklessly, cutting her off, swerving, all this she thinks they do on purpose, she thinks everyone on the road is doing these things on purpose to get her in an accident.. and she will call me, to tell me all about it… calls me in the morning and throughout the day, calls me when she gets off, and any time even when she is not driving but went to the store or is with her boyfriend and he does something… She will call me and rant about it for literally 30+ minutes and then, something else happens, and another 30 minute rant, and then she will bring up what happened ealier that she already ranted about and rant about it again. For another 30 minutes… and then the next person she sees that she knows, even though i listened along she will jsut repeat the exact same thing. i dont think her mouth stops moving ever. And she cant ever eat because shes so stressed what everyone is doing. I have tried listening and just being supportive and agreeing or challenging some of these “purposeful acts from these people” Maybe they are in a rush to work too, maybe they dont realize they are going slow. And she brings up well she does that too but she at least tries not to and these people arent trying and clearly doing it on purpose. I am fine with venting and ranting, I even do it too, i get it sometimes you had a stressful day, or a stressful or weird event happened, but this is…excessive.. I dont think i ever hear her talk about her self or her plans or anything, its always that something’s has happened or these people did this they did that… i try to reason with her or set boundaries like, hey you are spending your entire day worrying about other people just let them be just focus on you..etc, but she just blinks or pauses and then goes” anyway” and continues ranting. She is seeing a therapist and even her therapist says things with her she says she agrees with but yet these rants and obsessions continue… I dont know what direction to go in to try to reason with her to stop this obsessiveness and focus on herself… I have tried setting boundaries like i dont want to listen to this i dont know how to be more nice about it , i have tried ignoring but she will find someone else to vent to and still is nonstop..