Critics don't like that Harley Quinn breaks the fourth wall, that the writers are turning her into the DC version of Deadpool.
Source: Harley vs Apokolips
I just started reading Girl In Crisis, and it gets into how her madness is causing a rift in realities. Personally, I love all these iterations of Harley Quinn. With Joker, without Joker, Gotham City Sirens, Birds of Prey, her Gang of Harley's, ad infinitum. As long as the writing is good, I'm good.
Here's how I see it. She has auditory and visual hallucinations, she is mad from past trauma and falling into the same white chemical that manifested Joker. For all she knows, she is just talking to the hallucinations.
Maybe that's because Deadpool is one of my favorite Marvel characters. Either way, I don't mind.
She's a comic book character, her story is going to change, and I'm sure there will be narratives I don't enjoy as much, but it won't destroy my mad love for Harley Quinn.