"Why in hells name did she get uninfested in the first place? Because Raynor wanted her back to humanity so they could finally be together."
You need to understand that while kerrigan was the Queen of Blades she was controlled by the overmind/Amons will. She had no control over her thoughts/ and actions. When we used the Xel'Naga Artifacts in WoL it cured her while also breaking Amons power against her as well as hybrids siphoning the energy to revive amon.