I can't believe this is even a question. No, she is not in the SLIGHTEST bit a Complete Monster. Her heinous level is insufficient (even Sunset Shimmer was worse than her when she got turned into a demon!), she and the other Dazzlings are all friends despite getting on each other's nerves, and the narrative considers her and her friends becoming harmless, normal teenage girls in the end to be a reasonable fate, meaning the possibility of redemption is left open to them and they're not to be seen as truly heinous villains.
One could make the argument that magic/energy absorption and violation of someone's entire being is horrific beyond generic villainy, though even then it's not quite as horrific as what the Tirek of G1 did or threatened to do to his victims.