I don't have a girl ekkie, just my boy, but I've done a fair share of research since I'd love a female some day, so fwiw...
The girls have a reputation for being territorial/cage aggressive. Consider their natural wild existence. Nesting spots are scarce, and once they find a suitable one, they tend to not leave and protect it. Multiple males will bring her food in hopes of a little action, if you know what I mean. They're not a "mate for life" species, and their mating season is totally opportunistic, so any time of year.
So in reality, your girl behaving like that is largely ingrained in survival instincts. Not to say that all female ekkies will behave that way, but it's known to be common. So, what do you do? Best practice is to minimize hormonal triggers. That can be a challenge for anyone, but I think maybe more so for the ekkie girls. (And yes, very much the boys too, they just... different)
And so, lots of uninterrupted sleep. 12+ hours, though many go with natural sun up, sun down schedule. Keep the sugary food to a minimum. That includes fruits. If your girl is a big fruit/veggie eater (and I hope she is) more veggies and small amounts of fruit. And then, limit access to places that could be considered a nesting site. Most of us here are not fans of huts and the like for that reason, plus many of them are some kind of fuzzy fabric that can cause major issues if they chew and ingest the fibers. Potentially very dangerous for them.
If you can keep her hormones in check, you may see improvement in the aggression/defensiveness. Best to work with her away from her cage. It's her home, her safe space, and you're the invader there. I've met a number of quakers that act much the same with their home, but were sweet birds once away from their personal domain.
Hope this is of some help. Oh, and if you'd like to share, we love pictures here, please and thank you. Those ekkie girls are so beautiful!
