first off, let me say that the story is interesting and believable; sometimes these things scare people so, i wouldn't take the comments to heart..
second, at first i thought it might be the baby itself; this is not that rare where a young child, even an infant, can exhibit paranormal seeming activity..however, the flying out of the window does concern me. a baby would want to entertain itself(not unlike adults ha ha); it would not get rid of the 'toy'. and, if it was some sort of entity, it may or may not require any metal to do it's 'show'
several things are apparent here. one, is that your aunt was meant to see this, something she needs to think about in general. you mentioned she has other children? does she have paranormal activity surrounding them, herself, etc? this particular baby might be of 'interest' to some, especially if this is a 'family trait'..
and--it may be aliens-related, it is hard to say..unusual for sure, and something, that if it were my child, i would look into and research more
here is a thread she might like, tho it does deal with older children; she also might try googling 'orbs' or something of that nature having to do with the kids...
anyway, i certainly wish you luck with this, and feel free to chat anytime..having a little one myself who is, ah..'unusual', i know what it is like to have 'unexplained activity' around lol