Maybe some of the fangirls are always jealous of Yuki, as a school girl, she is so lucky that there are so many handsome and beautiful Vampires around her, and the two main boys Zero and Kaname have feelings for her, which probably is one of the main reasons that so many cosplay girls are obsessed with her.
Vampire Knight Yuki also have simple hair style and costumes, one of the typical pieces is the black and white Day-class girls’ school uniform, which is also the most popular anime dress in the eyes of the girls. If you are looking for easy cosplay but also wanting to be recognizable and beautiful, Yuki Cross would be a good idea.