I just had a flight with SilkAir where there was a cabin crew member dressed impeccably in all black whose sole role appeared to be to observe different members of the crew performing their duties from a 5 ft distance. Throughout the whole flight she shadowed a different crew member. At no point did she perform any service task that I could observe. This was my first flight with them in several years. How unusual is this ? It certainly raised eyebrows from passengers.