johannah, welcome to JWD. You've seen first hand how JWs treat their less fortunate like Kathy. Those JW elders believe that disfellowshipping her was a loving thing to do.
If you become a baptized JW and have the occasional relapse by smoking for example, you too will be disfellowshipped and your sister will never be allowed to speak to you again.
Each year, tens of thousands of JWs around the world are disfellowshipped. Some for smoking or having sex before marriage. Others just for disagreeing with the elders.