Jo held up her hands at Molly's slightly defensive tone.
"Hey, that's between you and Sam. I'm not going to run and tell Dean on you."
She would, however, try to lightly nudge Dean to give Molly more of a chance. She understood his concerns, but in her mind Molly had earned the right to be trusted.
"I'm glad Sam's helping you. I think you two could be good for each other."
Sam needed someone to talk to just as Molly did, though if Molly didn't know about Sam's trip to Hell then Jo wasn't going to be the one to betray that secret. She would let Sam reveal that to Molly on his own terms. She was just glad that Sam was letting someone in.