Complex sentence: She also begins to doubt whether she is truly human anymore, and upon learning that Bhunivelze also stole Serah's soul from her and manipulated her memories, plans to betray him when the new world is formed.
Split into simpler sentences: She also begins to doubt whether she is truly human anymore. Upon learning that Bhunivelze also stole Serah's soul from her and manipulated her memories, she makes plans to betray Bhunivelze when the new world is formed.