This is the grandmotherly Vargr who owes personal loyalty to Holmes for the favor of getting her psychotic corsair ex-husband sentenced to be spaced. In fact, the "Baker's Streak" is her husband's former corsair vessel. It was supposed to go up on the prize vessel auction block after his capture by Holmes. However, Mycroft arranged to have it sold back to Mrs. Hudson for one (1) credit, on the understanding that she would lease it to Holmes and Watson for a sum which just happens to match it's operating expenses. With no other means of livelihood, Mrs Hudson accompanies the vessel as Holmes' valet-cum-surrogate-mother.

[NOTE: I stole the executed ex-husband reference from the first season of BBC's Sherlock.]