Hey same song. A few things to think about in order to adjust your approach.
First ding is right, since she has already affirmed to you that she believes they are "God's chosen organization". Ask her questions like why does she believe that? What sealed it for her? When did they become so? Etc...
These are important things to talk to her about. Not just flip flops. Flip flops are explained away exactly as she has done so. Most are minor, and quite frankly, all religions make minor flip flops on certain things. This is too easily explained away. You have to focus on the indefensible. Blood doctrine is a good place to start. Bloodguilt, the inconsistancies of the blood fraction allowance, and the fact it is enforced through communal shunning. Its like the mafia. Once you in, you can never get our without taking a bullit. Because of that you just want her to take her time.
Talking to her about wether the people are really happy or not is another losing battle. Yes there are actuall happy JW's, and many are fantastic stand out people. You don't know all of these people and their belief system seems odd to you, but she is developing friendships that she didn't have before, and that is a powerful motivator. Lastly, the religion does NOT BAN organized sports. So when you make comments that are not true, or are embelished (they certainly say they are a bad idea), you look like the unreasonable one.
Deal with facts not fiction or eaggeration. With reality this strange you don't need it anyways.