This question has been bugging me for quite some time to be honest. I mean, I understand his actions for why he did it, but I don't fully understand why he had to blind her.

You may seem a bit confused when you cross this question, let me explain:

~ I understand that he blinded her because he said, "If she didn't like what she sees, than maybe you shouldn't see anything at all." So, therefor, she shouldn't be able to see the torture to the mermaids if she doesn't like it.

~ But, out of all the things he could have done, he chose to blind her. This leaves me wondering: Why? You're one of the most powerful wizards of that day, and you simply blind her? Aren't there worse ways of torturing a free thought princess? Blinding her seems like the good end of the deal: She could leave and see Faragonda, have her eyes back to normal in a flash.

~ I know, blinding her seemed to be the only "interesting" and "appropriate" way to let her earn her Enchantix, but you could have done something better. We all knew she was going to get healed anyway, so, why not do permanent damage?

Sorry for my rambling, and if you still don't get this question, feel free to comment or move on.

She shouldn't see anything at all, everyone should know THAT.