In part 2 of Charmed Again, Pheobe & Piper decide to save Paige because no matter what she is still their sister, and like Piper said, blood is thicker than evil.
Paige finds out she has magical powers, which are cool by the way, due to the fact that she's half whitelighter.
The source surfaces so he can try & get Paige to use her powers for evil, and Cole goes off to look for him & gets stabbed by the Source in the process.
The end was my favorite part of the episode. The sisters finally begin to accept that Paige is their sister & welcome her into the family, then they take her back home with them to meet Patty for the first time.