Well. Lets say serenity dies. Kaboom. Titans cry, some random crime lord takes the blame. Titans get all emotional and want revenge. 

Serenity wakes up with jack standing next to her. She is in a room and feels weak of course. Then Jack says "I just killed you. Yet here you are. Another thing the complex can do. We brought you here to prove one single point. Your teen titan friends never came to help you."

So remember, there is medical equipment that can culture blood. I'm not sure how great her healing factor is but what if that cultured blood regenerates back into serenity. Then, she finds out the titans didnt even try to save her and she joins jack for the sole purpose of revenge.