Actually it would work if 1 of Jon or Jaclyn jump ship. Jaclyn could tell Josh that they need to split the vote in case the other side have an idol. Josh side would have 7 votes right now, so they would split the vote 4 for 1 person and 3 for the other.

On Coyopa they basically split the vote every time in case someone had the idol.

Jaclyn could realize that Jon isn't going to jump ship and she could think that this could be her only chance to send one of the guys home.

So instead of Jaclyn being a number for the 4 vote or 3 vote, she would go to Jeremy side and be the 5th vote in that alliance.

So the vote tally could be either one of these 2 options.

5-3-2
5-3-3
( Depending on whomever Jaclyn was supposed to vote for. Basically how Rocker was going to do if Josh didn't find out and change his vote to Val. )

That could be also the reason why her confessional for next week is "Somebody is not going to be happy."

The reason I think that is for Jon/Josh is because she didn't say that about Jeremy last week when she knew he would have left.