They've actually slightly improved this lately, they ask about what they determine are risky sexual behaviors (ie hookups) with no gender attached now. The one thing is that you can't be actively taking PrEP and donate because it would obscure the HIV testing results (that they ought to be doing every time, multiple times!).
Source: https://www.redcrossblood.org/donate-blood/how-to-donate/eligibility-requirements/lgbtq-donors.html
Anyone thinking that lemmy is a welcoming space to women should read through that thread first.
Edit: the current state of Lemmy and the fediverse reminds me heavily of early reddit, for better and for worse. You can curate some pretty supportive communities if you are careful picking them out, they remain well moderated, etc. But there are plenty of places where you'll get scummy content if you wander or if posts attract too much attention.