AJ has been wearing that lightning bolt pendant since she was on NXT season 3. Way before Punk started using it when he became leader of the New Nexus.
It's like their brother and sister in real life away from their characters. It's weird. They like exactly the same things, have knowledge of these small time comics that only like 50 people know about, and same goes for old time video games.
It's actually quite weird how much they are alike. He's like a male version of her and she a female version of him. So I don't know what the lightning bolt means but I'm nearly certain it has nothing to do with any type of Punk/AJ story the writers are trying to hint about. It's just something to do with the things they like I'm assuming.