This may actually truly be me seeing something that isn't there, but I'm not willing to rule out the possibility that it means something. *G*
When we get the horrified reaction shot when Sam first sees Amelia, and it cuts to her, this is what we see, for a split second:
Tell me that's not a halo.
And a RED halo, at that, though I think the white thing (which is also halo-shaped) behind her head, and the white light glare ameliorate the red somewhat. (Okay, I did not mean to make that pun, but I'll let it stand. *G*) She moves from right in front of that spot, so the effect only lasts for a second, but even when she moves, she's still got all that red wall behind her. That much red wall is never a good sign in this show.
Actually, I've been using the term halo, since I first started noticing all the red in the show, to describe something that we see directly behind or at the side of somebody's head, very close to or touching their hair, like red lights, or a red sign, or the tall back of a red diner booth, or even, as in this photo, a red wall. Sometimes there are halos of different colors, but the red ones always ping for me, and they pretty much mean Trouble with a capital T. I've never seen anything this blatant, though.
This one is also unusual because it is literally the brightest lit thing in the shot; everything else is indirectly lit EXCEPT that very round patch of wall directly behind her head. We're supposed to notice that shape.
(As a side note, because somebody really should have warned Amelia about Sam Winchester's Amazing Peen o' Death, I really want to see a music vid to Jen Titus' O Death using all Sam's romantic encounters. Hey, maybe that's why she's got a red halo! She'll soon be singing with the angels! Or, you know, something.)