Jacqueline is the best friend of Max.

After trying to kill the series antagonist the Reaper, a large dark figure monster bent on killing everyone for the betterment of humanity, with Max, she was almost killed and then kidnapped and forced to work with The Reaper for fit his goals. She was tricked into believing that working with him is the best option in the long run so she can be with Max(not in a creepy, obsessive way).. Even though she is thinks she might be doing the right thing, whenever she sees Max she still feels guilt for what shes done, but shes bad at hiding it.