Appreciate the prompt replies.
noidea_77 - unable to see the disk in disk management and also cannot read the external HDD ...
popatim - She did not do the proper eject - she just plug it out. I tried to save some files on her Mac into the HDD and it worked. Sigh ... seems that she has indeed formatted the drive
Moving forward, any solutions (cheap and affordable - less than USD$50) to recover the data ?
Thanks again !!