Switch to Silvia, then do Slo Mo and Replay followed by Close Up. Then, punch the enemy for three times the damage.
Get the Blue Cool Kick power up. Then while in battle, use Blue Cool Kick (while in the air, hold Down, and Kick). She will use a diagonal kick, then use Slo-mo, Replay, and Zoom in. This will do a lot of damage. Note: This works well against Bosses.
Whenever playing as Silvia transformed, double jump into the air and rapidly press Punch. She will slowly fall to the ground while firing her gun. This is useful when facing multiple enemies.