Truth be told, Spike doesn't need much manipulation.
Slither has two sides. She can be sadistic, petty, sarcastic, manipulative, contemptuous, impatient and incredibly greedy to the point where one has to wonder why she doesn't turn into a big monster like Spike did.
On the other hand she helps her loved ones in times of need, comforts her siblings in bad times and turns extremely vengeful when others upset or hurt her kin. Slither is observant, resourceful and cool under pressure. She is also playful and curious. When she causes trouble she always finds a way to foist her blame onto others.