The most amazing Miss Hudson joins the family, as Joan comes home to find her not a client, but a mess. A mess Shelock didn't talk to her about. The "roommate thing" discussed more presentely than the fact Miss Hudson has a Adam's apple. Sherlock is right Joan has no problem with it, but Joan is right this is their home now, the polite thing to do is to ask before - not after - the fact.
And ask he does, the next morning when Sherlock asks her out on a blizzard to solve their latest case, of course Joan is not going to dress in front of an audience. A qualm their turtle Clyde doesn't share, happy to pose the latest fashion as a fake ambulance in their model crime scene. By the end of the episode they have solved the case, Miss Hudson's love life and Clyde almost gets a habitat. You can't have everything in life but, for the time being, life at the Holmes-Watson household rings as close as perfect as it can be.