In front of of our line-manager one of the staff members said something quite nasty to one of the other staff.?

She said to this colleague "have you got eyes in the back of your head?" and the other person said "what are on about?" so the other member said "because it looks as if your staring at me when your not, do other people actually say this about you". Is this colleague joking or being downright spiteful because the line-manager didn't pick her up on it after.