Selección del último registro de INNER JOIN y agrupación

Disculpe mi sintaxis si es un poco incorrecta, pero probablemente intentaría algo como esto.

SELECT people.id, 
       people.avatar, 
       people.firstname, 
       people.lastname, 
       LEFT(msg.message, 90) AS message, 
       msg.seen, 
       msg.date 
FROM  people 
INNER JOIN (SELECT message, seen, date, sender_id
                FROM messages GROUP By sender_id 
                ORDER By date DESC LIMIT 1) msg
                ON people.id = msg.sender_id
WHERE      reciever_id = '". $user_data['id'] ."'