This video goes through several characteristics of a Mary Sue many that Bloom does not fall under. The only one being a tragic backstory, but her backstory doesn't affect her storyline till Season 3 and first movie at least majorly it doesn't affect the path of the story. The powers of hers affect her storyline more than one occassion in Season 1 and 2 why is that it is obvious Bloom probably has long term amnesia which means she is unable to recall traumatic events right away or even peaceful memories until they're triggered by sounds or sights she suddenly encounters. Like Daphne's voice was trigger, but it wasn't a tragic trigger, it was a very peaceful trigger. In this way her orphan story gradually grows into the magical story we got. That's what makes her stand out from other orphaned protagonists in other films and shows. I can actually name one female protagonist who is not an orphan and that's the leading female in the Hunger Games Katniss, but I never watch it too violent for me to embrace it on screen, Skylights. But Katniss stands out because of that I'm pretty sure most MC heroes girls have little to no parents. I know Natasha never knew her real parents either. Long term amnesia can also be the case for Icy, Darcy and Stormy straying so far into darkness which in that case Bloom is a direct mirror to her enemies' reasons for becoming dark and evil the difference is she decided not to get consumed by it in Season 3 unlike Icy, Darcy and Stormy did which caused them to end up tearing each other down and fight over a maniac of a villain man whose attention ended up pointless and worthless for them.
Secondly there isn't just Post Traumatic Stress Disorder they is also Complex Post Traumatic Stress  Disorder (stuff that keeps bugging you haunting you on repeat, guys. Doctors won't say it is a condition, but it is a condition.)

Bloom has Childhood Long Term Past Amnesia because at the time of the war with the witches on Domino the world underwent the influence of an Earthquake thanks to Darkar that is what made the palace sink and in later scenes we see she starts developing Complex Post Traumatic Stress Disorder which includes includes inability to remember some members, and having difficulties being able to regulate emotions when around others. The memory loss also states memory of trauma will resurface at times and cause substantial distress. Bloom does have panic attacks and loads of anxiety present in the first two seasons of Winx Club in fact I say she went through two Corruption Points one that was Physical and One than was Mental (Season 1's second half is her Mental fall into Corruption) Season 2's halfway through was her Physical Fall into Corruption Point right now.

Problems I have with Stella
#1 She is a basic blonde rich kid, love of shopping, into beauty topics, very vain, and adores the topic of fashion and gossiping about boys and their girls. Also she is a bit naive leaning towards Stereotypical motto that I've seen too many times in movies. Only two times in the show have we seen her lose control about things,  both which were under the influence of spells both hypnosis- 1 twisting her words, the other controlling her mind. For 1 time in Stella's performances on screen make her mess up for the full episode on her own not because of Students or witches, because with the fairy powers even it looks like she is way too OP and Perfect of a Character you want a Mary Sue character to Challenge the character decision ignore Stella's fairy power and she acts like a goddess disguised in human. She's more op than Bloom right now.  She never messes things up very often which is a problem, because characters shouldn't be perfect. Two blonde extreme generalizations blondes are too dumb, innocent and naive, or they're too pretty and too smart basically smart alecs something woman in general are often called nonstop, stop please.

Hope you enjoy this I enjoy Stella in Season 1 & 3, and Season 4. I didn't in Season 2, Season 5, Season 6 since it was too similar to plottine of the 4kids dub in Season 1 in the 9th episode. Season 7 was meh, and Season 8 I cannot say anything about as I have not seen it. Don't have access to it period.