I absolutely agree with every point you make here, in addition to a couple things.
I do say this as someone who hasn't read her in the books, and I really do hope that there will eventually be a bit more silently communicated androgyny in her appearance, however:
a) she is dressing up for Lestat right now, which in the book (if I recall correctly) is established she dresses more femme when he's upset. If this is femme for her, what a treat!)
b) she is still violently upsetting gender roles in her own way, even outside of the use of the Incest motif. All of those visual cues of her resisting certain traditional gender presentations in American and European culture that you listed definitely fit, alongside her personality which is awkward in being nurturing.
Within the use of the Incest motif, however, it is unignorable that she is upsetting gender roles. There's a reason the incest is there, and it's not for whatever naysayers are saying about shock value or misogyny. This is a story, there are reasons elements are included stories. There is a LONG tradition of Incest in the Gothic genre being used to communicate sensations of disturbances to societal constructions of gender roles and desire. Mother-Son incest is the most queer of the heterosexual incest depictions specifically because of how much it challenges what assumed character traits genders should display. There's a reason I keep talking about it, and there's a reason she is inseparable from it at the moment.
It's not like using Gabriella in a newly sexual manner should be completely unexpected, considering how Lestat was written in season one, but it is still absolutely in line with how Anne wrote these vampires and their Maker/Fledgling bond in the first place, in addition to the logic of all of the adaption changes that have been consistent through the show (Gothic Incest, Jenny DiPlacidi 279):
This whole show has been specifically about melodramatically exposing systemic violence and the institutions of power. Gender and Sexism is 100% part of that, and Lestat is raising the melodrama with the exact tonal shift we should have been expecting.
c) if people's expectations of queerness have to be loud and immediately visible, what are they then saying about Louis's feminine attributes -- chosen and performed by Jacob? Because Louis doesn't wear more obviously feminine cuts to his clothing, is he not feminine enough? Of course, that has been an ongoing war in the Loustat part of the fandom as long as I can remember (I only get highlights from my few mutuals who are Loustaters), but Jacob played Louis with Ertha Kitt, Grace Jones, and many more iconic women of color as inspiration specifically to create a sensation of Gender nonconformity without having dress the part. If he just wanted to play Louis as gay, he would have, but he specifically chose to emulate cultural icons. Louis and Gabriella already have many parallels in their personality traits, why can't the same connection be given here?
We've all praised the writers' ability (at least I hope we all have) to write simultaneously within the absence of metaphor by exposing societal horrors and injustices plainly, AND with depth and subtle gestures to make this show worth the same amount of effort you're willing to give it. There's a reason it's complicated, AND worth discussing in good faith, especially if certain writing decisions are hitting you wrong at first. Gothic Horror isn't an easy genre to experience, it never has been, and that means we should be patient with ourselves, and with the story as it continues to lay out what it wants to tell us.
I've said it before, and I'll say it again, Gabriella is testing a lot of people's internalized misogyny by not hiding everything about her femininity, yet is clearly confronting everything a woman should be. She isn't supposed to be representing the Divine Feminine, that'll be Akasha's job when she arrives, but she is visually representing a certain type of white woman who comes from an affluent high-class background, and there is visual language and intent with what the writers want to communicate with that. If that's how Gabrielle is dressing for Lestat to perform femininity, let's look closer at that AND reflect that this would be very nonconforming to the societal structure Gabriella would have had from her point of origin.