LightPhoenix said:My new loony theory, which is so rediculous that I'm sure it's wrong, is about Jessica.
Jessica, like Peter, absorbs powers. Except, whereas Peter does it in real-time, Jessica only does it when they die. She also gets some of their personality.
Okay, I'll call that one loony, alright.

My thought - the whole Nikki/Jessica division is a "normal" psychological problem. Nikki could not deal with the death of her sister, and so created an alternate personality to help her cope. It just so happens that, being the tough one, Jessica is the one who figured out how to use the super-strength. But, like Isaac and drugs,that's a psychological block she may be able to break. If somehow Nikki can deal with her trauma, she'll get rid of Jessica, and have her powers to herself.