This episode was more revealing to the sisters in the fact that instead of wasting so much time focusing on private matters, they have yet again found themselves playing catch up again.
The sisters, more so, Piper and Phoebe, because of experience, should have known that Christy was a Trojan Horse waiting to pounce. They should have known that the ultimate power was Billie to start with. For starters it was really way too easy to finally find Christy after all of these years, especially when Billie remembered all of a sudden of a sister missing. And another telltale clue is that Christy shoots fire. Duh...Can we say demon here?
The sisters should have just faced it after dealing with the Zankou crap that "normalcy" isn't just them. They are magical and that means dealing with the magical community. If they had treated the magical community on a more personal level instead of using them only when they need something, things would have been a little better, they would have probably not have bailed on them like they did.
Overall, the writing could have been better. I just hope the next episode and the finale are much better.
Oh, how I will miss my girls...May they be Charmed Forever!!!