When I first read 1984, I was struck by how assertive a character Julia is. It is she, after all, who initiates the relationship with Winston, and she already has a fully developed set of political principles before he even speaks to her. In some ways she is a lot like Clarisse in Ray Bradbury's Fahrenheit 451.
Just about everyone is subjugated in this novel. Now that you mention it, I wonder if Big Brother is always male. Is it possible that sometimes they have a Big Sister? Somehow that doesn't sound as frightening. I guess it's the lack of alliteration. It could be sexism!
The idea of patriarchy seems fairly strong in 1984, especially with the figure of Big Brother. One way to get specific with this theme is to ask - Are there any female figures of power in the novel?
As post 2 says, there are no females that have a powerful figure in the novel.