Looking at the picture of Ella and Tanos again, I'm now completely sure that Ella knows MC from the hospital that he was taken to after his mother's death, the same hospital Dad took him after the fight with Kenny. The hospital itself is probably connected to SIN, they are the only other players we know that know a lot about monsters, considering that, I'm going to assume that that is the same hospital Kenny's father runs (We know he has dealings with SIN from this update). It's also possible that the hospital belongs to hero, Tanos was probably working there under his father at the time, this would explain why mc dad would bring him there, since we know he has some connections to Dexter, and why hero knows so much about Ella. Xanthe saying that Cole was a recruit taken by Ella plays into that, Ella was probably held in the same hospital with her future lieutenants and broke out of there with them. But if it doesn't belong to hero, then Kenny's father was monitoring and taking tests on MC right after he had killed his son.