I agree. Dogs need to sort out the pack order by themselves. Only interfere when things start to get physical (i.e. when you start to hear vicious snarls). It is also a good idea to intervene when you see visible tension such as raised hackles and the stiffness that you described.

Whenever you have a small and a large dog, I will always recommend a muzzle. Even though my greyhound Giselle was the submissive one, I muzzled her nonetheless. Big dogs don't understand that their sheer snapping strength can snap the other dog's back. Therefore, I would definitely recommend a muzzle for the time being.

The mistake that you made was allowing the dogs to meet on their own territory. Like you said, Violet spent enough time in the kennel to regard that as her safe spot. So when Bailey intruded upon her space, she felt the need to snap at him. You should have introduced them on completely neutral ground like the neighbor's yard or a nearby park. Perhaps you can reintroduce the pair tomorrow at the city park or something. Keep a slightly loose lead but always be on the lookout for aggravated dog behavior. If the dogs sniff each other but do little else, praise and treat them. I wish you luck and post tons of pictures!