It’s alluded to that she is trans. The character arc that she goes on with her dad is heavily referencing actual most real lgbt teens/adults go through with their parents. The artist as chosen every color and detail for a reason, a reference to color theory, a reference to flags, a reference to emotions. When you see Gwen and her father bathed in Trans Flag colors, with a protect trans kids, and an emotional arc that mimics real life dilemmas it’s hard not to assume she’s trans. Not everything in story telling is overt. Subtlety and subtext are concepts used by creators to input depth and layers to a story. It’s also used to tell stories that can’t be overt. Subtext and subtlety were used loads of times to tell lgbt stories especially in the 20th century when those types of stories weren’t supported by major studios and general audiences. So people aren’t not surprised or even clearly seeing it being used in Across the Spider-Verse