she's with her boyfriend near bill's house by the water of course.
Keep in mind the is in Cerulian city
she is in the cerulian city, psypokes.com offers a great walkthrough
you find her in the cerulian city gym
You can find Misty in Pokémon Crystal in Kanto Region. You will find her north of Cerulean City where she is with the man she is dating.
At the outside of the sea cottage To get there go to cerulean city then go straight ahead to cerulean cape then go left and battle the eight trainers and beat them all then keep going left until you find misty then she will return to the cerulean gym when you get back to the gym the other trainers and the man you always meet in the gyms will be there too
It will be in misty's gym close to the entrance.
The second gym trainers for each generation are as follows: Pokemon Red, Blue, Yellow, Green, Firered and Leafgreen: Misty, a water-type trainer Pokemon Gold, Silver and Crystal: Bugsy, a bug-type trainer Pokemon Ruby, Saphire and Emerald: Brawly, a fighting-type trainer Pokemon Diamond, Pearl and Platinum: Gardenia, a grass-type trainer
I guess Ash will marry Misty, because how I know is I heard Misty's best friends are her togepi and Ash. Even in Misty's Song Ash and Misty sounded romantic. Besides Misty is one of my favorite Pokemon trainers.
you go to cerulian city then head north and go across the bridge. after you cross the bridge, head east to cerulian cape. there are trainers that you HAVE to defeat so bring good pokemon. when you get to the end, you keep following the path, go up the stairs and there will be misty and another person. she will call you a pest for interupting then challenge you at her gym. then you have to go back and battle her to get the next gym badge. hope that helped ;D
Go up the bridge in the northern part of Cerulean City and beat all the trainers where the bridge gets off. Travel east (or otherwise to the right) and you will see Misty.
after you get the macine part and return it you go up to bill's house
Go north of the gym on the long path, then go east through the maze of people. Then you'll see Misty and her "lover". He'll leave, then you'll talk to Misty. You can now challenge Misty.
It's in one of the pools of water in misty's gym