That's one I haven't heard before! Sounds like the bank has told you to get a POA from the embassy. What if you simply removed your fiance from the Purchase Agreement and Mortgage? You could only do this if the loss of her income would not effect your abiltiy to perform on the mortgage however. Maybe you could ask the sellers to move the closing back a bit?
Let us know how it turns out please.
Thanks and good luck,
ALL the Best
Dave & Lisa