Courtney did better then people think at the challenges. Firstly, jumping into the green jello didn't actually matter. Even if Courtney accomplished it, the Bass would have still lost the challenge, as only DJ, Duncan, and Sadie completed their challenges. Even triple points would not have changed it.
In the other challenges, Courtney did well. She came in 3rd for the Bass in the Awake-a-thon, did very well at dodgeball (as well as coercing Duncan to play), she had a talent lined up for the competition (and Chris mentions she was their strongest competitor) but Bridgette ruined it. In the other challenge, what she did wasn't spotlighted, but it didn't hurt the team. Plenty of people, like Harold or Izzy, did worse for their team.
I doubt she would have won the challenge, as she would have refused to do many of the dares when it came down to the final three, but she did have a solid alliance with Duncan though. Geoff and DJ were close to them, and Bridgette seemed to be close to Courtney (the two of them were dishing on Geoff's bad gift together.) The guys would have chosen Harold over her because Harold was aggravating them with his slopiness.