(Real) Estate agent(s)?

IMDb lists one "estate agent" in the cast but, assuming that's what we in the U.S. call "real estate" agents, there is one at the beginning before they buy the house and one at the end when Billy's grandmother is taking him for his ill-fated ride. (Or if an estate agent settles estates the "first" one is settling the estate of the previous owners...)

Although they don't look alike to me (from the brief scenes each has) I wonder if they're the same person? I wonder because the last scene shows the agent looking up at Billy closing his bedroom door and she's smiling, continuing down the stairs even though she waved goodbye to Alice's mother and Billy minutes before... so why isn't she at the very least puzzled, even alarmed, when she sees Billy?

If they are the same person this would lend credence to David's belief about sacrificing children (which I'm somewhat sketchy about -- he mentions it to his co-worker but I missed whatever he saw that gave him that notion), and explain why the agent smiles up at (dead) Billy. David also mentions the agent who sold them the house lied about the previous owners, a family whose mother set fire to the house, killing her son. This would further strengthen the "child sacrifice" claim although the movie doesn't seem to make it much of a plot point. And, of course, since Alice is pregnant when she's murdered (and she and her ghost fetus avenge their deaths by drowning David... rather over-the-top IMHO), yet another baby is sacrificed, albeit pre-natally...

If it's 2 different agents I still wonder why the second one isn't surprised that Billy closes the door upstairs after he's left the house.