B767 Flight Attendant reported during cruise flight experiencing an aircraft vibration and loss of altitude. The flight crew reported an engine failure resulting in the flight diverting to another airport where they landed safely.

Narrative

During first break there was a shuddering/vibration that I had never experienced before and myself and another person woke up and looked at each other with surprise. Then it happened again and along with that the nose dipped and we lost altitude for about 5 seconds. The passengers were screaming and FA Person A came and woke up the purser so she could talk to the Captain about what had just happened. The purser notified the cabin crew that we had lost an engine and were turning back to land in ZZZ. The Purser made a wonderful very calm announcement about an incident with the aircraft and we were going to ZZZ to assess the situation and it was going to be a 'normal' landing and that we had 45 minutes until we land. The cabin crew completed cabin checks and took our jump seats. FA Person B was the only FA that sustained an injury. Also no seat belt announcements were made nor was the sign on during this time.