Riley's story was even more heartbreaking than Allison Young's (the human Cameron was copied from).
There's a scene where Riley enters the hotel room for the first time with Jesse, and she's overwhelmed by the luxury and objects, smiling like a kid in what was a pretty regular room.
(There's a similar scene when Derek and his crew arrive from the future and just stare at the LA skyline, mesmerised.)
That summed Riley up. She was, in a sense, rescued from the future but was out of place and time in the glorious past. It was tragic that she couldn't bring herself to admit what she was when John asked her if she needed to explain anything to him. She just couldn't bring herself to do it. Jesse only had one goal, to break Cameron's hold over John, and she worked Riley remorselessly.
When Riley finally snapped and attacked Jesse, she damn-near made things right. I believe Jesse only shot her out of desperation, but Jesse wasn't a sympathetic character, so no sympathy for her plight.
And what a great actor's name: Busy Philipps. Despite being around 30 at the time she played a school student pretty convincingly.
Annoying, and out of place. Hell they only added her cause network wanted John to have a gf. Glad they made something interesting out of her story arc.
Her character and Jesse's character were written like crap. Maybe they are both better actresses in other shows, but on this they were both pretty irritating. To be honest the most irritating character was Sarah. The series had some good ideas, but suffered from bad writing, and directing. That's why it isn't on anymore.