I really couldn't understand why Jack saw her as Torchwood's humanity, the one to remind the rest of the team of what it meant to be human, since she seemed to be the embodiment of some of the worst human qualities. It was as if Jack wasn't actually seeing Gwen, but someone she reminded him of, someone who really was everything he seemed to think Gwen was, if that makes sense. She seemed more a liability to the team than a help, she apparently didn't even know how to hold a knife safely and quite frankly, that made her look stupid. Any policewoman would knowe you don't hold a knife with the blade sticking out. It meant I couldn't believe in her as an ex-police constable. If she'd been some sort of journalist, she would have been a more believable character, someone who doesn't know about chain of command and the importance of following orders, or about weapon safety.