I kind of understand some of what she desires. Luke isn't always going to be in the same party, and if there is ever a monster that his sleep magic doesn't work on, they will need that experience to grow stronger. But the issue with worlds that have a level up system is that you can also become stronger by simply killing some creatures. Now, manga and manhua worlds like this definitely lean more into the idea of "having a higher level is only an advantage that strengthens you, not makes you invincible," but such an experience shouldn't be forcibly applied by personal views. It should be an event that takes place naturally, or at least be artificially made by someone with real experience.