It’s been a while since I’ve had to touch it too. But couldn’t Alice provide Charlie with both the plain text and her public key. Charlie could then encrypt the text and see it came out the same as blob Bob sent Alice?

Typically end to end encryption includes digital signing of the message so you can verify who the sender was.

Yeah, end to end encryption means its not possible for someone to intercept the message between person A and person B. Nothing stops person B then forwarding the message to person C to report it.