J.W.
You have all the right to feel uncomfortable about your friends behavior, because it is in fact extremely inapproproate. You called her one of your best friends. If in fact this is true, there should be no problem with you bringing the issue to her attention. You can't keep hiding your soon to be husband from her. If he has noticed the extra attention and it makes him as uncomfortable as it makes you than the issue needs to be brought to her attention.
You can deal with it in a non confrontational way. Just simply tell her that the way she behaves around your fiance is inappropriate, list specific examples so she is completely clear on the behavior that needs to stop. She may be completely unaware that this behavior is making you uncomfortable.
Friends are there to make your life less complicated, and she seems to be adding to your stress level. You already have so much on your plate.
Good Luck!
J.