As said in the comments, Erika is not meant to be viewed as an entirely evil character and the truth not meant to be painted as an evil thing, and as such the Trick Ending is not meant to be a straight up "Bad Ending". The point of the two endings is a matter of leaving it up to the reader should Ange choose to seek tangible results that uncover and conclusively, definitively establish a truth of life in the material world she lives in or choose to live by her own spiritual truths even if they're intangible and not entirely definitive or conclusive: it was never a black and white issue.
The manga, Golden Fantasia, and Last Note Of The Golden Witch flesh out the Ange-Beatrice and Erika partnership more and it's actually meant to be a very grey thing as well, not strictly an "evil" thing. Ange, or rather Ange-Beatrice, becoming more like Erika is not her "turning evil", it's her, jaded and traumatized by the past as ever, deciding she wants to pursue a future as an investigative truth-seeker and in doing so become a person who can make deductions so thorough that she'll believe her reasoning to be flawless and reflective of the truth (just as Erika is prone to doing), and once she's reached that point, no arguments from anyone else could ever dissuade her or hold any power over her. Erika being with her is symbolic of her keeping her darker nature at her side at all times and, as they're both witches of truth, they can both be merciless and even cruel but also keep each other in check as they search to uncover and establish the full scope of truth with all possible truths weighed and considered, the right way rather than the "neglect the heart and focus entirely on the ends that their means will reach" way like Erika used to do prior to her and Beato's game in EP6.
titsay
yousharknotpass
turnnoffyourmind
theartofmadeline
romaincrisis
