Responses
1. There actually isn't any proof of the villainess using dark magic, it's just stated that she's a very good magic user. 2. The villainess isn't as dumb as you think considering she's been hiding her dark magic from the tower & the people. Even Eru failed to find out twice even though he did a thorough search. 3. If she uses the excuse of "I've seen the future" then she would be in more danger.
ITS NOT THAT HARD, JUST TELL HIM SHES USES BLACK MAGIC OMLLL. Why don’t these people ever use the “I’ve seen the future” trick and tell them what’ll happen. It’s frustrating how they both KNOW that witch is using black magic but won’t communicate with each other.