Let's have an honest conversation about Diaspro. This young lady was done dirty from start to finish. She was raised and trained throughout her entire childhood to be Sky's wife and queen, yet she's then turned into the villain after Bloom attacked her unprovoked and Sky two-timed her.
The show tries to justify this by having Bloom mistake her for Icy despite the fact Diaspro and Icy look nothing alike except for the fact they're both blonde. It then glosses over the undeniable truth that Sky has actively cheated on his own fiancée with Bloom despite him being well aware that he's engaged to marry Diaspro and he has been betrothed to her since they were children.
We learn in a later season of the show that Sky and Diaspro were also childhood friends. If Diaspro was so horrible, and Sky such a nice guy, would he have ever willing been friends with her? (Well, he's a lying cheater who's never once suffered any actual or lasting consequences for his own actions, so it's a possibility.)
Granted, the things Diaspro did after the initial reveal were all wrong. Teaming up with Valtor and the Trix was a horrible decision, but it was also a choice made out of desperation, fear, and righteous anger. Diaspro was literally brainwashed for most of her life to believe she had to be Sky's wife. Diaspro's never been given or known any other life goal, option, or way forward except for the one laid out for her by her parents and Sky's parents.
That does not justify her actions but does help us understand where she's coming from. Neither Bloom nor Sky once offered her any apologies for attacking or cheating on her. They literally got away with their wrongdoings while Diaspro's entire life and reason for being was turned upside down. We later see in her interactions with her parents that they were livid Sky chose Bloom over her, and instead of consoling or comforting their daughter, they scold her, complain about all of the money and resources they have wasted on preparing her to be his queen, then demanded she win him back or else.
Yes, Diaspro needs to check herself and work on herself. She isn't a great person. That being said, she wasn't born a villain. Sky, Bloom, and her own parents twisted her into one by their words and actions. If Sky had been honest from the start, a lot of nonsense could've been avoided. It was only after he'd been introduced to and dated Bloom that he suddenly had issues with his arranged marriage to Diaspro.
He kept a picture of Diaspro in his dorm at Red Fountain. If he didn't have any feelings for her, why bother keeping her photo there at all? My guess is that he wanted to have his cake and ice cream, but the girls crossed paths, and instead of coming clean, he let Bloom assault his fiancée in the hopes they'd be too busy seeing each other as rivals to realize he'd wronged them both.
Bloom also stopped being a victim when she went out of her way to attack a girl she didn't know and then kept dating the guy who two-timed that same girl rather than confronting him about it/apologizing to the girl she went after for mistaking her for someone else and assaulting her.
Diaspro gets a lot of hate from the Winx Fandom, but while some of it is earned, people tend to forget that she wasn't the active cheater or the little homewrecker who ruined someone else's life. Her entire future was planned out for her without anyone asking what she wanted, then the position she'd been raised, trained, and brainwashed for was taken from her by a girl who had no issue with dating/wedding a lying cheater who was already spoken for.
Do I think Bloom did Diaspro a huge favor in the long run? Yes. Sky has shown he's capable of infidelity and deceit when it suits him. I honestly think that Diaspro is better off without him, but she doesn't see that do to all the warped teachings of her own parents and their society that've been instilled in her from a young age during her formative years. She needed to step back and take time to decide what she wanted instead of just saying/doing what everyone else expected of her.
To be clear, I'm not in any way excusing or endorsing the evil or underhanded deeds she performed later in the show. The girl needs to be a better person. I'm making an observation and pointing out some things fans either failed to notice or glossed over while reading the comics and/or watching the show.
Diaspro is a victim and villain because all of the wrongs committed against her were never even addressed let alone rectified. Bloom and Sky never once tried to apologize or make amends. People say Diaspro's a monster, but they also refuse to acknowledge that Bloom, Sky, her own parents, the queen and king of Eraklyon, and Eraklyon society (which is an absolute monarchy based on a partially medieval aesthetic) itself are responsible for the creation of that monster.
On a side note, Sky has proven to be a terrible friend, horrid boyfriend, and will probably suck as a husband. Diaspro dodged a bullet.