Incog Nito In Norse mythology Loki is a shapeshifter (internal and external) a gift that he has past onto Alex, shown by the fact that Loki is her mother and not her father, Alex also says in the book that she doesn't always have control of the internal shift
Leela W. It's already been proved in the book that Alex doesn't like her father. She wouldn't do anything that he told her to do, so it must be her choice 100%.
sam being genderfluid isn't a choice, it's how you're born. the way loki conceived alex could very well be a factor in her gender, but i find it more likely that she's genderfluid just because she is, just like anyone in the real world who has a gender-expansive identity.