According to Jim Recap: The Bachelor
When Dana is chosen to be on The Bachelor, she feels that she has finally made it. She can be herself and land the man of her dreams (Doug Savant plays the bachelor). Jim is the first to mention a potential problem, that being that guys don't always like it when girls act like themselves. Luckily for Dana, she listens to Jim for once, and hears what he says when he tells her to ask the guy about himself and his mother. So when the conversation starts to fade, she takes Jim's route and reels it back in.
The next night, as preparations are made for dinner (and Cheryl goes a bit overboard as she tries to cope with everything going on around the house), Jim and Andy try on the headsets, and when they do, they overhear a conversation that they shouldn't. Dana's new friend is planning to dupe her into a one night stand, then dump her on the show the next day. While being nice to Dana isn't their normal course of action, that's okay for them - not for someone else, and especially not on national television, so they hatch a plan.
While Cheryl and Dana are away, they corner the scheming fellow in the bathroom, away from the cameras, and tell him just how psycho Dana can get, and how he needs to get out of there before she sinks her claws into him or he will regret it. They spook him just enough so that he runs off before dinner is even finished. Of course Dana is upset, but in the end she finds out why and it's a very happy ending indeed.
The original Bachelorette Trista Rehn shows up in a cameo at the end as a graduate of the University of Jim.
