She was, and she wanted to be regent in case the child she was carrying (who turned out to be Anastasia) was a boy.
Yeah, it was a tricky situation, since if I read Witte's description of events correctly, the succession laws made no provision for an unborn heir, which meant Mikhail Alexandrovich would've become emperor immediately, however, if Alexandra then gave birth to a boy after Mikhail had succeeded, it was earnestly hoped that he would step aside in favor of his newborn nephew, while Alix and he would serve as regent.
Out of curiosity, this is probably a self-explanatory question, but Nikolai originally abdicated in favor of Alexei, but then when Nicky was told to pack his bags as he wouldn't be allowed to stay near/with his ill-son, he protested that "he cannot live without him" and abdicated for both of them. Why wouldn't they let Nicky and Alix have supervised visits to their son? And was that even legal (Nicky abdicating in Alexei's name (I know Alexei wasn't of age to rule yet, but not even Napoleon abdicated in the name of his son; ICR about the Comte de Chambord, if he signed the document himself or his uncle or grandfather did for him)?