Livre d'Or

I don't think discussion / reminder of gender discrimination is out of place in queer spaces. If anything, it's important to talk about the intersections between different marginalisations (like your Black woman example, or we could also consider religion or disability). In addition, a lot of anti-queer discrimination seems to be based in gender discrimination and/or a sense that people are violating gender norms.

I think it's categorising the gender discrimination as discrimination against straight people that feels out of place in a queer space.

Thinking about your niece: if we assume up until her declaration of pan-sexual identity she was assumed to only be interested in boys and dressing accordingly, lots of women who love women dress more masculinely, so maybe that's what she's exploring. Certainly I've always felt more comfortable when my overall presentation neither entirely feminine or entirely tomboy, whether that's very long hair with jeans and tshirts, or very short hair and long flowing dresses.