I forgot to mention that she also had a living brother: but he was heir apparent to their father, Emperor Pedro I of Brazil, and eventually succeeded to the throne himself as Emperor Pedro II.

Like I said, historical observation has it that females do not easily inherit thrones in the living presence of male agnates -- no matter what the law officially states. Indeed, if it came to that, laws typically evolve from default and circumstance -- as in England.

All agree that the Salic law could never have worked there, as it did in France: females have been able to at least transmit succession rights to males from the very beginning -- inheriting the throne and ruling only since the Tudors. As it was, Queen Mary I was not the married mother of a son in whose favor she might have been pushed aside.

Nor did she have a paternal uncle or cousin: that being said, it's conceivable that if King Henry VIII had a surviving younger brother and nephew through him, he might have arranged a marriage between his daughter and that hypothetical nephew -- thereby securing the English throne in the hands of the Tudors.

Queen Maria I of Portugal, in fact, married her own paternal uncle (something not allowed in England) -- thereby keeping the Portuguese throne in the hands of the Braganzas: they became joint sovereigns (her husband becoming King Pedro III).

But if the living male agnate in question does not have a throne himself to occupy, female succession is typically met with resistance -- as witnessed in the Miguelist and Carlist wars ensuing from the accessions of Queen Maria II and Isabel II, respectively.

The more distant Bourbon relations of the latter had thrones in Italy (Parma and the Two Sicilies); but Uncle Carlos had nothing to inherit but the Spanish throne which he thought was rightfully his after the death of his brother, King Fernando VII.

The separation of the French and Navarrese crowns was a foreshadowing of the separation of the British and Hanoverian crowns in 1837.