I'm not sure how to say this without risking being condescending or mansplaining to you, but...I think it's likely that this is going on around you to some extent without you realizing it. Harassment can take a lot of forms--and what's even more common than outright harassment is just being treated or thought of differently.

There are also varying standards for what qualifies as being mentally categorized differently--things that I and others here would notice and that you might not. For example, I'm one of those people who disapproves of using the term "females" as a noun, like you did in your OP, when you're just talking about women or girls in general. In the grand scheme of things, using "females" as a noun instead of as an adjective is a pretty small potatoes issue. But if I were hanging out in your guild chat and people were referring to women that way frequently, that small rhetorical trend alone would give me the impression of a community that isn't as inclusive to women as it could/should be. (And if you don't get why, it's basically because it's a detached and dehumanizing way of using the word.)

Anyway. I honestly don't know if my comment here is even a good thing to be saying to you. I'm torn--between wanting you to know without a doubt that these challenges are happening for women all around you, including in-game--and not wanting to drag you down with my cynicism, especially with what you've been through in life. It sounds like you probably do have a great guild and have been overall very lucky in your online experiences so far. So definitely cherish that.

As to your theory that it has to do with play-level...unfortunately that's not the case either. See this documentary about young women who are tournament-level CounterStrike players who have to sit in their own special corner and only compete against other women.