Have you found anything to make you believe that she's still cheating on you? Via facebook or her text messages?
Of course you're jealous, if you weren't, you wouldn't care if she had cheated on you. While she needs to earn your trust again, you are at the point where you are putting out feelers to see if she's worth trusting again. You want to give her a chance but you also don't want to revisit the emotional pain that you felt when you found out she was cheating on you--after all, once is MORE than enough.
Wondering if she's still hiding something from you will probably always gnaw at the edge of your thoughts until you come to a point where you either have to deal with accepting that she made a mistake and won't do it again or accept that fact that you can't believe that you can ever really trust her again. It may take a long time before you find yourself trusting her again.
Perhaps looking at her facebook and checking her text messages is a sign that you don't believe she's told you the complete truth. If that's the case, it would probably be wise to confront her.
If she's honestly trying to fix a terrible mistake that she's made, she'll tell you everything, no matter how horrible it is. There's always the chance you'll leave but it's probably a greater chance that if she hasn't told you everything that eventually as you find out there's more to the story, your distrust of her will grow.