When I worked for HAL I brought my then girlfriend onboard and she stayed in my cabin, and then my parents came onboard later on a reduced rate cruise for family and friends and stayed in a veranda cabin just underneath the bridge (so I could keep my eye on them!).
The girlfriend quickly discovered she didn't like my life at sea, and so a few weeks later I met a new girl who was working onboard and is now my wife!

There are two types of entertainers with HAL, there are the permenant staff assigned to a ship for I believe around 8 months from a company called Stiletto, but unfortunately they share cabins and live in pretty harsh conditions.
The 'Guest Entertainers' who tend to be higher profile entertains tend to come onboard for much shorter periods of time, and often rotate around ships and even companies or brands. They tend to be treated much better, have excellent cabins or guest cabins and completely seperate from the crew. My suspicion is that your friend is in this catagory, and if so will have plenty of space to accommodate you and I'm sure you'll thoroughly enjoy the experience.