As soon as you try to attack her, she immediately blocks it. She sends all of her magic on you and although you and the slime put up a good fight, you are defeated. The Lady of the Manor walks over to you and instead of merging with you, she is impressed by your use of magic and she decides to make you her apprentice.
She changes you and makes you subordinate to her. She also changes your attire to fit more her style and she removes the slime from your body. Since the slime already removed most of your memories from previously before you entered, you are left with your only memories being with the Lady of the Manor as your master. Overtime you accept your role as her apprentice, you learn new magics, and you even get to have some fun with the occasional intruders.