There's gotta be mind control or something going on. She has the ability to copy anyone's ability.. that seems to be a clue. She's an elf, so if MC is an elf, and is able to control other elves as an extension of herself at will..
OK here's my theory. Childhood friend is who the homunculus are based on. That's why they have a strange obsession with MC. They have a piece of her existence within them as their base operating system. Maybe she was in an accident when she was younger and her parents were involved in this...
If you think about it, a man who can hold his liquor, who doesn't have violent outbursts when drunk or otherwise, with a mild tempermant and hard worker.. she probably pushed for the marriage more than her father.