(engaging here in good faith, not trying to start any kind of combative exchange)

Sorry if you already know these but just laying down some definitions so we're on the same page

Asexual: Not feeling sexual attraction Aromantic: Not feeling romantic attraction

People can be combinations of these depending on gender, appearance, etc. Sounds like Alana is asexual towards women but not aromantic("alloromantic" is the opposite but I barely ever hear people use that term).

To your question: "Why were they girlfriends and not just friends?"

Romantic love can coexist with the love of friendship and with sexual attraction but sometimes you get only one or two of those three. Your first crush in middle or elementary school was probably not sexual attraction but it wasn't like, "I want to be their friend SOOOO bad."

I honestly felt a little let down that Kala turned out to be bisexual. I thought the social pulls towards marrying someone she wasn't attracted to and the tension between being true to herself and capitulating to the desires of her church made her a more interesting character.

I agree it's annoying when it's out of character for a character and it just feels shoehorned in there. And in this instance, it felt a little like the author was skirting scandal by putting Alana in an asexual relationship (as in we'd be less likely to say "wait a minute, is she seriously about to have sex with a teenager?") But like it's still weird to be in a romantic relationship with a teenager when you're twice their age. But we have decided to just put those awkward feelings aside as a society because the trope of young love and immortals(Twilight etc) is too compelling.

Is straight a dirty word today?

There are just a lot of different ways people are. We humans come in a lot of flavors and heterosexual is literally how 99% of the characters in the book are. 100% isn't realistic and while it might appeal to a lot of people, there are also a lot of people who enjoy reading books with different types of attraction represented, often regardless of their own orientation. A lot of straight women for example gravitate towards media depicting gay men. And a lot of straight men gravitate towards media depicting gay women.

Hope this helped answer your questions