While calling herself a demon and acting like the villain, Homura isn't actually evil, all of her actions were due to her love for Madoka and to grant her and everyone else a better life. She isn't exactly happy with what she has done but she will keep playing the part of the villain as she needs to. Her power allowed her to rewrite the universe and create an ideal world where Madoka was separated from her God self and where everyone is living a better life. 