Based on Bertha's pov so far (which you can find here):
I don't think she's evil like some people theorized at the start, but I do think she is misguided in her efforts and will accidentally end up bringing about the Big Bad of the series.
Because, let's face it, her sister wasn't a good person. We already learned that she permanently cursed Bertha to throw her out of the competition, but she also apparently permanently cursed Mertha out of jealousy.
She sounds like a petty person as well as just an overpowered dangerous kinda threat. And Bertha is trying to summon her back.
She's doing it to break hers and Mertha's curse and for revenge which is fair enough for the most part. But I do think she'll end up regretting it










