The story went like this.
Misty received a phone call from her sisters, requesting her to take care of the gym while they were gone on this trip. Even though her sisters came back, she's still at the gym.
She came back for two episodes, then she left. Again.
Some think she may come back again to stay someday. Some think she isn't. I personally don't think she is, but that's just me.
And no. She didn't tell Ash she loved him, or vise versa. -_-