If the Fangs lose immunity again (which they probably will), they should get rid of Kelly, but they should do it by voting for Sugar. Here’s how it should work.
The four original Fangs (GC, Ken, Crystal, and Matty) vote for Sugar. Kelly also votes for Sugar. Ace and Sugar will vote for Kelly. Sugar plays the hidden immunity idol, the five votes against her do not count, and Kelly is removed from the game...and Sugar no longer has the idol.
If the original Fangs vote for Kelly, she’ll be removed from the game and the results will be exactly the same...except that Sugar will still have the idol.
Won’t Sugar have to play the idol before the votes are counted? (I always have to think about that.) So, they would have to tell Sugar they were voting for her or she might not feel compelled to play the idol. On the other hand, if they do tell her, she might think it’s just a ploy to get her to play the idol while the real plan is vote for another player.
You could go crazy trying to figure all the permutations.