I would feel just the same in your shoes. I waved one of my granddaughters off on a 14 month travelling adventure. That was nearly 3 years ago now. She reached Australia and decided to stay. She now has a job, an apartment and a lovely life in Brisbane. It saddens me that young people feel the need to emigrate for a better life. They should be able to get a good life here but successive Governments have put paid to that.
From now until departure day you will have to continue to be a good actress and keep smiling and being supportive.
Who knows, one day, you might be Australia bound to either visit or join them permanently. I really feel for you. 