can someone explain that last part? what will she do in the end?

Last part? As in when she mentioned possibilities?
When the sorceress mentioned that "If" she wanted to stay, they could support her, Eris then thought to herself that it's a possibility that won't happen, because she would never want to stay, in that world, but simply talking about it and humouring the thought was pleasant enough and she enjoyed discussing possibilities with the sorceress

thats it! thank you <3