Most people think Bloom is cause she has everything and everything is always about her,
1- A boyfriend who is a king and the strongest and best specialist of red fountain
2-A king and queen as parents,
3-A sister who is the most powerful nymph of the magic dimension,
4-The most powerful magic in the whole universe'(the dragon flame),
5-She is a princess,one of the most popular fairies of all time,
6-A pet lol (kiko),
7-Her parents are the founder of the Company of Light(Oritel and Marion),
8-She defeated all the villains,
9-All her friends always worries about her,
10-She is a singer,
11-The villains always want something from Bloom or her family(Season 1&2:THE DRAGON FLAME,Season 3:To kill her or torture her,The Secret of the Lost Kingdom:Also to kill her,Season 5:Her sister's powers, Season 6:Her powers or to kill her again)
12-She formed the the Winx Club
13-She is always in the spotlight.
14-Her boyfriend is the typical prince charming.
15-She is the main hero and the other Winx are her sidekicks
Well here are some reasons people think she's a Mary sue but i am completely against it.
I love Bloom as a character and I also love the way she has grown since season 1.
Bloom in season 1 had low self confidence because she was scared that she might lose her best friends and her parents and she didn't believe in her self.
Trough the seasons i watched Bloom grow in many different, she is now capable of sacrificing herself for others and she would do everything she could to save the people she loved and also the Magic Dimension. She is not afraid of telling her opinion or the face a new enemy.
She is hard at forgiving herself for trusting the wrong people as seen in Episode 10 when she almost feed poison to Flora but she was able to overcome that problem by believing in herself and also thanks to her best friends.
Bloom has always been grateful for having Stella,Flora,Musa,Tecna and Aisha as best friends and she knows she wouldn't have been able to overcome all these problems and her owns without them.
So basically I don't think Bloom is a mary sue, she is just an ordinary girl who happens to be a princess and the keeper of the Dragon Flame with great friends, caring sister,loving birth and adoptive parents, enemies and a wonderful,lovely and caring pet rabbit named Kiko!