Is it necessary to inform a friend after secretly returning embezzled money to him, given that informing him might lead to losing him?

It is sufficient for acquittal from this money that you return it to its owner in a way that he knows it is his money. You are not obliged to inform him of what happened as long as you fear scandal or harm. It is sufficient for you to return the stolen item to where you took it from. Conceal your deed, and congratulations to you on your repentance and regret for what occurred, for Allah accepts repentance from His servants.