I think your problem here is -
There is a trainer in the town that you have to talk to who tells you that the cape is a good spot for dates. He also mentions that Misty likes to go there sometimes. If you don't talk to him about it, she wont spawn.
Also, if you triggered the Suecune event thingi BEFORE you did the generator, you have to capture it BEFORE you can battle trigger Misty. Since that section is used for two events, you have to do them in order.