awl,,,, i am so sorry for your loss... and so sudden...
dogs do also mourn and get depressed so i understand your concerns. i had two GS and lost one, mine were brother and sister and Ollie was devastated when losing his sister. he would almost refuse to go back in to the backyard and still does not like to go without me.
I immediately changed up his (our) routine.. if they were super close like mine were, and if you are missing her, you know she will be missing her too.. so if you can, just try to change up the routine, take her on walks, car rides, play games with her, enjoy time with her. She will also be able to feel your emotions on missing her and may feed off of those as well.
Just be there for each other.. it is the ONLY thing that helped me through my loss.
Good luck, and again, so sorry for you loss