>>280305192
She was tortured for years by dark elves who wanted to exploit her healing powers. MC hypnotized her as part of his scheme to rescue her, saying, "I've made her my loyal dog and she'll only heal me now". Sadly she's so traumatized that she subconsciously refuses to return to normal even after being rescued. Her mind maintains the dog persona as a coping mechanism.
The good news is once they remove her rivets she'll be healed instantly, as her passive healing is so OP she can regrow lost limbs. However that's on hold for now as chopping off the rivets (they fused to her skin) would only traumatize her more.