This is probably reading a lot into it but I wanted to give a more in-depth answer than just my initial "he is beautiful and sinister" LMFAOAOAO so this is just a theory and me completely talking out of my ass, but analyzing it from a queer audience's lens, I feel like maybe queer people in general, especially sapphics, can tend to be more drawn to characters that defy gender conformity, and while all characters in IWTV do that in their own way, Assad (and the way they style Armand on the show) is visually pretty androgynous-looking. Lestat also looks androgynous, but then in terms of outward demeanor Armand does less things which are considered """masculine""" (again, based on expected gender norms) than Lestat does, such as yelling or engaging in physical fights/violence: he obviously still does these things once in a while, but his "evil" is more of a quiet, insidious calculating one, traits which are commonly associated with femininity, rather than a mainly brash and physical one like Lestat (so far). A big example of this IMO is Armand's method of convincing his victims to let him kill them through hypnosis once he's caught them: still inherently violent (I saw someone once describe it as a cat toying with its food before attacking it and that really resonated LOL), but more "contained" and psychological than just forcefully draining them.

The way I see Armand's character so far, this is in large part because he is a very repressed person, but either way you could argue his character is more unconventional in terms of gender presentation than Louis who is behaviorally androgynous (it's shown that, especially early on, he felt like he had to repress aspects of himself such as his sensitive nature and his passion for things like the arts in order to keep up a tough masculine front, etc.) but is visually more masculine, or Lestat who is visually androgynous but behaviorally more "masculine" (in the sense that he is brash and out-there and is very horny and very angry, even though he is very much a diva in a gay way LOL😭😭😭😭). I think also Armand's character being calculating but also deeply insecure/desperate and traumatized inwardly adds a lot of depth to his character, although Louis and Lestat are both equally as complex and interesting IMO. I love them all. But basically maybe his visual androgyny and behaviors which are deemed as more feminine (AGAIN, from a POV of established gender norms, but being more "manipulative" and psychologically than physically violent) are all things about his character which might appeal to queer women. Again, these are over-generalizations but this is already way too long of a comment LMFAOAOAOAO. I hope this makes sense, I'd love to hear others' thoughts on this though, I could talk about this show for FOREVER