my bet that the scene the abusive dad had of the future (or past regression, idk) where magnolia went full villainess mode was her using some kind of innate monster charming gift to control monsters and destroy everything, hence why he imprisoned her and why the monsters were dropping presents for her and were confused/not attacking. i think there's a pretty good chance we'll get monster companions at some point, especially if this is a territory building series like the title suggests
the line where she says "isn't reincarnation usually where you get some amazing powers or something" followed by the ant confrontation seems like very on the nose foreshadowing for this