That is so awesome! I can't answer your question about her acting like a young pup again at 3.5, but it's got to bring joy to your heart to see her so full of life and energy again, especially after the surgeries.
BTW, Buster does that exact thing...stands at the back door to come in and then runs off when I open it. Silly dogs!
Beth, single mom to three skin sons and
Buster (6/6/08), flashy brindle M, docked & floppy
and Ruby (9/14/11), fawn F, docked and floppy
Samson & Sheena and Sezar & Sadie - all at the bridge