Why does Savannah (7 months) scream bloody murder whenever someone leaves the room?

She just started doing this about 3 days ago.
My daughter and her two older kids, Brande and Aden, will all be in the living room with the babies, and if any ONE of them leaves the room Savannah just WIGS OUT. I just called Corrie and Savannah was just screaming bloody murder in the back ground. Corrie had just walked into the kitchen to fix her a bottle. While I was on the phone she finished up the bottle, then went back into the living room and was saying, “Savannah! Look! Here I am! Savannah!” Savannah instantly quit screaming.
I know about separation anxiety, and object permanence, all that kind of thing, but this is a bit extreme to me! Do you guys have any ideas?
I told Corrie she needs to put a big picture of herself on the wall!

Also, Savannah has been around my dogs many times, but just recently she started expressing fear when the dogs (especially our big shepherd) come around her.