My Lands: Black Gem Hunting

A player sent me a message from one account saying that she has another account on the same server and in the same clan. Is this sufficient evidence to issue a ban for multiboxing to the accounts?

The message below is the message with the player's name removed:

"xxxxxxx also my profile ... I sent you movie"

please, report the message to in-game administrators using the Report button in the original message.

So, if I built up a big account, gave it to friend who then played it from their house in a different location on their computer.
Then a few months later would I be allowed to return to the game, starting a new account or would I get banned?

You are allowed to play a new account. The main rule is that players are allowed to possess only 1 account at any given time.