Actually as someone who has gone to school both in the south and in a very conservative area, sex ed is scarce in some places. I can totally believe she didn't know better back when she got knocked up with Rylee, especially when you consider that she dropped out. Now, after she moved out west, there is no excuse other than willful ignorance or her being too stupid to know how to use Google.
Yeah, she ditched Rylee with her mom and took off for Seattle, where she got involved in a social/creative scene where being GLB was completely unremarkable, T was still pretty rare but hardly unheard-of, and "genderqueer"/"pomosexual" variants such as androgynous, agender, and ambigender were still a fringe-y sort of thing--but definitely a thing. Granted, back then she wouldn't have been given a pass to be in that last group because she's such an obvious cis female who has no inner conflicts with presenting herself and acting according to feminine social norms. She's a total ultra-femme "girly girl," and always has been.
Seattle may not have been SF, LA, or NYC a decade ago, but it sure as hell wasn't Laurel, Mississippi, and Tess would have had to be living under a rock to be unaware of her other sexual options while living there. If she was sexually interested in other women, she would have had plenty of chances to discover that--the burlesque/pinup scene has a lot of femme dykes, as well as bisexual women, in it. Ditto, if she was into "girldick." And yet all of her relationships as far as anybody seems to know have been with cis, straight men. Funny, that.
I've known straight women (from as far back as the late '70s), who went through a "lesbian" phase after getting out of really bad relationships with men. I'm sure women are still doing that, under the mistaken assumption that women can't possibly be as toxic and abusive as men. But Tess isn't even doing
that, as part of her rebound from Nick. And while it was never considered cool, back when, to turn dyke in order to avoid shitty men (everyone else understood it was just cope), these days it's practically expected of anybody who wants to be cool to claim a much more complicated sexual identity than they actually possess. Tess could have claimed she was bisexual; it would have been not only expected, but
almost believable. This "queer" shit, though? LOL, NO. Not from somebody who is totally okay with being a hyperfemme cis woman, who is obviously only interested in manly cis men with big, thick...bankrolls.