It's been established since chapter 1 when her mother says she could compete with men if she had magic (which she clearly does). And the premise of the manga is clearly that Eva wishes to be the strongest and will do so, in case the "Becomes Unrivaled" part of the title isn't clear enough for you. It's a fantasy comedy manga about an overpowered princess, lighten up a bit.
The mother said, "Fighting is a man's job - if you had magic then, it could be possible...but a girl, fighting..." All that tells us is that with magic the mother thinks that a woman at least wouldn't get steamrolled by most men. Since most men likely don't use magic that isn't saying much.
Also I was describing physical strength not fighting power. As far as I know there has yet to be anything that indicates that women on average are equally as physically strong as men. (All other things being equal.) The MC is so physically strong because of 4 reasons. Genetics, training, past life memories, and being the MC. Unless the basic understanding that men are physically stronger on average then women is presented to be different in some way in the story world vs real life I'll be assuming it isn't.
This doesn't mean I'm looking down on her. It's the exact opposite. She reached the level she did even with lower physical strength potential.