I'm going to play devil's advocate.
I honestly hope they make it. I understand that she's immature, and she needs to think things through but I wouldn't go as far as calling her gross. At least she dyed her hair for after the final rose, right?
Honestly, if their relationship doesn't work out it's not because she's immature (I'm 24 too!) I think it's the show. It hooks us, we watch, and that's the point. Statistically very few bachelor's and bachelorette's have made it. To me this show is just a show. Real people are put on this show but when they leave this fantasy land where everything is romantic and planned out for you, and when put in the real world with real life challenges, it's a real test of the relationship which not very many survive.
And I agree with the person who said that these people really wanted 15 mins of fame. Why else would they go out to "find love" on TV?
Side note, not a strike at anyone, but does ABC do psych evaluations to make sure the people on the show are stable enough to realize what they experience on this show to an extent is not reality?