Our lawyer in Bulgaria e-mailed me this this morning-
"During this last week I have been in constant touch with the Embassy. Your I-800 is actually here but they don't know what to do-whether to let me go and do the provisional filing or waiting for the Supplement 3 and your daughter's fingerprints clearance to arrive too. They said that technically, they should let me do the provisional filing since she doesn't turn 18 before the end of June and is currently 17 but at the same time, it is a precedent and they are not sure. I told them I am subscribed to all precedents lol! Anyway, they said they would do is e-mail the DOS and ask them what to do. As soon as they have an answer, or if your daughter's fingerprint clearance comes (whichever of the two happens first), they would let me go and do the provisional filing. I will keep you posted."