I really don't think that is the case, to start i don't believe Ella's affection for Mc is because of being her chosen, since we learned that they have met in the past it's clear that Ella is fond of him because of whatever happened between then before the start of the game, if anything being her chosen made her like Mc more.
I know that we have no idea about what being her chosen even means, but from the way she talks i think she knows that her plan will lead to her ultimate death, and her chosen will be the one responsible for taking it over after her demise, in fact "take everything from me" i think means absorbing her or something similar but at the same time sharing her ideas and finishing what she started.
The "you can do whatever you want with me" is in the context of what would happen if Mc opposed her, and that reflects her way of thinking, that you need to be stronger since it's the way to make things happen, i doubt Ella could be convinced to give up on her plans with words, so beating her is the only choice, and if he does he can do whatever he wants because that is his right.