Halloween is a time where your girl and several of her friends get together and have fun collecting candy from the neighborhood. Wouldn't it be grand if she and all her friends simply dressed up in costumes based off a similar franchise? The Girls Group Costume collection is a page that features several costumes from a similar genre or franchise that your girl and her friends could choose from. They'll all look great dressed up as their favorite characters from a television show or movie.
One particularly well known franchise is the Monster High line of dolls and web series. These characters are based off classic monsters from novels and movies and have been redesigned as teenage girls who deal with the same kind of issues as normal girls. These characters wear interesting outfits and have body features similar to the type of monster they portray. Frankie Stein, for example, has green skin, visible stitches, and neck bolts.
Other popular characters who would fit the requirements of group costumes would be the Disney princesses and several others. The girls will all be going out together and enjoying the day, and having them be one group of characters will help make their bonds of friendship stronger. They'll forever associate the characters they portrayed on Halloween with each other.