Why does a male bastard have a stronger claim than a female true-born daughter? Why did Sansa not become the "Queen in the North"?
Theoretically, a true-born unmarried daughter would take precedence. And practically, if she were married to a strong ally, she and/or her husband could take precedence.
But Sansa's been married once or twice, depending on whether or not non-consummation can be perceived as an official annulment (in our world, it wouldn't. It's grounds for an annulment, but it still has to be granted by the church). So, at the moment, she's actually either a Lannister or she's Lady Bolton. And neither Tyrion nor Ramsay would be considered rightful Lord of Winterfell either by the Northerners or by Sansa herself.
If she is Lady of the Dreadfort (since Ramsay Snow pretty much eliminated all the other successors), then she is, in her own right, a bannerwoman of the North to Winterfell, much like Lyanna Mormont, and should now control any of Ramsay's surviving forces.
If her marriage to Tyrion is still valid, then she's a Lannister, which doesn't exactly further her claim, although it could open up some interesting connections for the North with Dany in future.
Remember, too, that "King in the North" is a very old title, one that was revived from before the Targaryen Conquest of the Seven Kingdoms. As the title goes back before Aegon I's arrival in Westeros, it's quite possible there's never been a Queen in the North, so it might not occur to the Northerners to have one now. If even Lyanna Mormont isn't considering a female ruler, why would all the older men do so?