Following the order of events, it's safe to assume it's Ella with Jake. Deryl was put under the same day the 2nd one appeared. I don't think Jake could get to Alice and make her lie about it while she's fully aware of him. Ella's probably keeping a close eye on him too since he's now in a position of power.
That said, Ella could do several things outside of Jake's knowledge. She does have the same transformation ability, obviously since she taught it to the MC. It is possible she planted a fake Deryl to be in the coma and the real one is with Jake. That requires a lot of effort though so I think she just transformed herself and pretended so she can watch over him.
Ella's honestly a wildcard at the moment. Since she's lvl 5 now, there's no telling what new ability she gained or branched from her current set of powers. For my own sanity, I'll just say she's Deryl in disguised with Jake instead of making a theory out of it.