I really liked this drama & how it wasn't so frustrating. I was worried they'd follow the trope of jealous women…
Yes, it's sad that the powerful her got controlled and even killed her lover in the end without herself knowing what she was doing. But all the shifters were Danju's and JinMu's puppets. They helped them to soul shift so they can control them using sorcery of Choi family (which JinMu used) So, it's possible, no matter how powerful she is, in the end gets controlled by that powerful sorcery because she is a soul shifter after all. But Naksu gets the happy ending she deserves with her loved one by her side in part 2. You can try watch and see the next season.