The thing was Greed did want Sloth to bow down and say she was gorgeous. This for Greed was him showing off his prize possession and no one telling him how awesome it was. That was what greed in itself was, showing off what he had. When his own family didn't take notice it was a blow to his ego.
"You look amazing," Digger said without even realizing he'd said it out loud. At least one person in the room was going to recognize it, but Digger was also human. Humans noticed Zoe more when they were around Greed because he made her that much more desirable. Around other Sins it was different.