What if what you had been working so hard to build up had come crashing down with one kiss.
Joan had tried very hard to keep her feelings down. She didn't even hint at them towards Sherlock. At first she did it because he was her client. Now that he wasn't her client, what was the point in hidding her feelings? The only reasons she could muster up were that it could ruin their friendship and any potential cases that would come their way. For those reasons, she kept her feelings hidden; very sucessfully, she might add. But one night, a snow storm, and a bottle of whiskey changed everything.