Dean's right when he says Jo's iron knife isn't worth much as a weapon compared to the one he offers her, but her knife has killed a good few nasties in her father's hands (and the compensation-issues knife of Dean's is harder to hide between sock and ankle); she'll stick with what she's got.

Jo hears no end of rumors, thirdhand from one or another hunter who's latched on to Jo's base as the sort of gossip hub that the Roadhouse used to be (which it can't be; Jo's the only one with hunter connections at that bar, and Minnesota hasn't nearly the central position Nebraska has), about the latest damn fool stunt pulled off by those crazy sons of bitches Dean and Sam Winchester; Jo takes note of every word, but every time she hears someone say they opened the Devil's Gate in Wyoming, or they're planning to go to hell just to break the gates open from the inside, or anything of that nature, she tells the speaker that she's met the Winchesters (usually whichever idiot's speaking hasn't) and she'd wager her reputation on theirs and her life on their skills.

Jo's heard Sam's psychic, exorcising demons without devil's trap or Rituale, and anyone who can pin down a demon without a careful trap can certainly open doors and trigger a bomb from a safe distance; she doesn't ask for the truth of this, though, and wouldn't ask him to do it even if she knew he could—if neither he nor Dean thinks it's worth suggesting, she'll trust that it's not, and anyway the suggestion would come across as asking Sam to help Jo force her mother to betray Jo, which would make her mother want to kill her—wait.