Sometimes RPGs have optional content that contains more powerful foes than the main storyline. While it would be nice to have said storyline scale up in response to your strength, some people prefer it not to: they prefer to feel their characters' power. (Sometimes I agree, sometimes it would be nice to have the final boss become stronger than the superboss if you beat him prior to the fight) If you're concerned about Mila power creeping out of control, try a playthrough where you tackle fewer sidequests and level up less. Slay fewer vampires/feed on fewer people, don't get quite as much good equipment.
See how far you can push it.