An easier explanation might be that Skynet has access to FBI files and that Ellison was the leading agent on the Connor case who spent years searching for them.
And he no longer is, as Cromartie should easily have been able to determine. So why keep following him?
Remember, the sticking point here is that even AFTER radically altered circumstances, Cromartie still thought Ellison would hook up with the Connors.
No, I do not think she is part of a third faction, her disregard for human live is way too high for that.
Erm, Weaver is a Terminator. They're specifically not programmed to have much regard for human life, at least initially. Both Cameron and Uncle Bob had to learn these lessons at some point.
Why would this change just because she's not on Skynet's side?
You know, I really wonder what Jessie and Riley's game is. They're blatantly manipulating Connor, not just driving a wedge between him and Cameron to "stop her" as they say, but also between him and his mother - they're making him a moron. Whatever their intentions are, it's not noble, from what I see.
Perhaps they don't regard Sarah's influence as especially important? John Connor is John Connor, and a fair portion of what he is has to be genetics. Either that, or they regard Cameron's influence as just THAT negative.
"Peace on Earth and goodwill towards men? We are the United States Goverment - we don't DO that sort of thing!" - Sneakers. Best. Quote. EVER.
Periodic Pwnage Pantry:
"Faith? Isn't that another term for ignorance?" - Gregory House
"Isn't it interesting... religious behaviour is so close to being crazy that we can't tell them apart?" - Gregory House
"This is usually the part where people start screaming." - Gabriel Sylar