....don't let on you know she is different, just lavish her with love, and if she's up to it, her favourate walks, and the odd treat.....if she doesn't improve, I would go back again to your vet for his advice
....the fact that she is so sad means either she is unwell/sore, or she has had a bad time and not liked it or has really suffered from separation anxiety.
....i have never left my 3 wee dogs, and have had to holiday in this country since i have got them.....they come too !
....it's now 7 years since i have been abroad.
good luck, and hope she improves soon....you must be worried sick !
Debra x x x x