Also, when characters are speaking - just a piece of advice - why don't you put them in speech marks and separate them with a line? etc.
"STOP!" Sylvie shouted, chasing after Team Psychic, anger boiling inside of her.
"Nope!" The first girl sneered back, continued to run as she stuck out her tongue at Sylvie mockingly as she laughed, along with the other two girls, holding Muffin's Pokeball up in the air.
Like that =) Makes it much easier to read.