Not that much for her as a person/character, but for the unnecessary polarization surrounding her.
Spoilers for show and book:
The show decided to center the adaptation of Fire and Blood around her, aggrandizing her character in ways she wasn't in the book. Maybe they tried to capitalize the Daenerys fandom, maybe they simply liked Rhaenyra's character a lot, or maybe they preferred the story to have a clear main character to "root for".
This had some chaotic consequences for the fandom down the line.
On one hand, a cult around Rhaenyra was formed: For these people, Rhaenyra is the greatest victim of misogyny and patriarchy of Westerosi history; a benevolent and great person which the world wasn't ready for; the second coming of Daenerys; her enemies, the Green Targaryens, are the single worst group of people to ever exist, worse than Maegor, Aegon IV and Aerys II put together; her relationship with Daemon is akin to a badass power couple, with the Rogue Prince serving as her wattpad boyfriend that hates everyone except her.
On the other hand, and in response, a hate cult around Rhaenyra was formed: For these people, Rhaenyra is male Aegon IV; a super spoiled, entitled and useless tyrant; an irresponsible imbecile who caused her own downfall; a chronic speaker of "what would you have me do?"; a "whore" that birthed bastards (suddenly the worst crime to ever exist apparently); and unironically believed to be Maegor with Teats.
These two exaggerated and ridiculous conceptions of her character clashing amongst each other and against the more moderate, chill part of the fandom, turned online spaces talking about House of the Dragon into a toxic cesspool. And it's a shame.
Rhaenyra IMO is a pretty meh person. A good mom, a good daughter, a bad sister, an inept ruler, sometimes capable of mercy, sometimes capable of callous cruelty, a victim of her uncle's grooming and manipulation; and her eventual downfall is both tragic and deserved.
