I question; what exactly Margaret is.  
 
At first I believed she must be a shadow because she had glowing yellow eyes but, upon Igor's words regarding shadow's having no place in the Velvet Room that little theory was broken.  
 
Besides the vague description of a "Servant of the Velvet Room" I do not know what Margaret is and the Megami Tensei Wiki only has a short few paragraphs on her. Due to this I am discouraged that there really isn't an answer, but before I give up; why not ask the largest P4 community? 

I think they just say that she's an "Inhabitant of the Velvet Room", which means she's just a supernatural entity of some sorts. They don't say exactly WHAT beings like her, her sister Elizabeth or Igor are.

Thats something that will probably never be answered...its just, how it is for Persona games.

This is just my theory, but following the games Jungian psychology motif, I think Margaret is the anima (feminine persona) of the main character.  This would be why Igor has a different assistant in Persona 3:  His different guest would have a different anima (in his case, Elizabeth.)
I also heard speculation that Margaret and Elizabeth might be the "ideal women" of their respective hosts.  This also ties in with the theory of the anima.
 
As for what Igor, I believe he is a universal archetype that exists in everyone's subconscious.  The Velvet Room is then a level of consciousness that only certain people can reach.

she is hot, thats what

" This is just my theory, but following the games Jungian psychology motif, I think Margaret is the anima (feminine persona) of the main character.  This would be why Igor has a different assistant in Persona 3:  His different guest would have a different anima (in his case, Elizabeth.) I also heard speculation that Margaret and Elizabeth might be the "ideal women" of their respective hosts.  This also ties in with the theory of the anima.  As for what Igor, I believe he is a universal archetype that exists in everyone's subconscious.  The Velvet Room is then a level of consciousness that only certain people can reach. "

She's a gold digger.

she's a bitch

It's not really clear where Margaret came from, but as you complete her Social Link, you eventually learn that she is the sister of Elizabeth, Igor's previous assistant in Persona 3.  Elizabeth left sometime between P3 and P4 for reasons that I can't explain as doing so would give away spoilers for the end of The Answer in Persona 3 FES.  Margaret stepped into her sister's role in part to find out what it was that that made Elizabeth feel the need to leave.

" She's a gold digger. "

" she's a bitch "

"This is just my theory, but following the games Jungian psychology motif, I think Margaret is the anima (feminine persona) of the main character.  This would be why Igor has a different assistant in Persona 3:  His different guest would have a different anima (in his case, Elizabeth.) I also heard speculation that Margaret and Elizabeth might be the "ideal women" of their respective hosts.  This also ties in with the theory of the anima.  As for what Igor, I believe he is a universal archetype that exists in everyone's subconscious.  The Velvet Room is then a level of consciousness that only certain people can reach. "

Every Resident of the Velvet Room is a Servant of Philemon, even Igor.

"Every Resident of the Velvet Room is a Servant of Philemon, even Igor. "

" @SmashedControllers said:

"Every Resident of the Velvet Room is a Servant of Philemon, even Igor. "

Yes, but does that explain who they are?  No, it doesn't. "

" @FluxWaveZ said:

" @SmashedControllers said:

"Every Resident of the Velvet Room is a Servant of Philemon, even Igor. "

Yes, but does that explain who they are?  No, it doesn't. "

They're Servants. "

" @FluxWaveZ said:

" @SmashedControllers said:

"Every Resident of the Velvet Room is a Servant of Philemon, even Igor. "

Yes, but does that explain who they are?  No, it doesn't. "

They're Servants. "

Potential Persona 3 Spoilers 
 
   Because she's a part of Aigis. "

" @FluxWaveZ said:

Potential Persona 3 Spoilers 
 
   Because she's a part of Aigis. "

What "

PERSONA 3 SPOILERS 

" @SmashedControllers said:

" @FluxWaveZ said:

" @SmashedControllers said:

"Every Resident of the Velvet Room is a Servant of Philemon, even Igor. "

Yes, but does that explain who they are?  No, it doesn't. "

They're Servants. "

The op was asking about their living state.  If they're humans or whatnot.  Saying they're servants doesn't answer anything.  Does saying someone's a slave mean they're no longer human?  No, that's incorrect. "