Peter Maximoff aka Quicksilver is the Rani. Here is why...
Super Speed = Time Lord Tech Edit
Whenever Quicksilver has saved someone with his powers, he has had his headset on. Obviously his headset must be granting him Superspeed. How could it do this?? Simple. It is Time Lord Technology.
Saving Himself Edit
Quicksilver saved Slowsilver from the Quinjet in Age of Ultron. How did he know? Because they both were versions of the Rani