Priscilla the Great Series by Sybil Nelson

Meet Priscilla Sumner, an ordinary seventh grader with extraordinary gifts. As if middle school isn’t hard enough, not only does Priscilla have to fight pimples and bullies, but genetically enhanced assassins trying to kill her and her family. Armed with wit, strength, and a genius best friend, Priscilla must defeat the Selliwood Institute, an organization dead set on turning children into killing machines... moreMeet Priscilla Sumner, an ordinary seventh grader with extraordinary gifts. As if middle school isn’t hard enough, not only does Priscilla have to fight pimples and bullies, but genetically enhanced assassins trying to kill her and her family. Armed with wit, strength, and a genius best friend, Priscilla must defeat the Selliwood Institute, an organization dead set on turning children into killing machines.Add an older brother annoyingly obsessed with Christina Aguilera, mischievous baby twin brothers who could scare the sin off of Satan, and parents more puzzling than a Rubik’s cube in the Bermuda triangle and expect a smoking page-turner! less

Hey there! It's me again, Priscilla, a lean, mean, tween machine. Just when I'm finally getting the hang of my powers, something even more confusing and harder to understand enters my world...boys. That's right, I can shoot fire out of my fingers and lift a car with one hand, but for the life of me I can't decode "boy-speak..". and that just might turn out to be the death of me.