I originally started this discussion under regional but need help from anyone that can give it! I had to put down my other dog this morning, from complications from osteosarcoma. Cash was a Rhodesian Ridgeback, & Annie's best friend from day 1. How do I help her adjust to life without her buddy?
We always had two dogs. How heartbreaking that she doesn't know where her friend has gone. I don't know what the waiting period is; that's up to you but I would get her another friend. In the meantime lots of love and understanding.
The best thing you can do for her is the same thing she can do for you, to be there. Dogs naturally know when you are sad, they will stay near you, they understand your moods and your thoughts and are there for you, they also keep you going, you have to feed them, you have to take them out, they may bring a toy. Dogs also grieve and this is as varied in animals as it is in people. In time you will both feel it less and being with each other is healing to both, nothing else is needed. In time you may open your home and hearts to another wonderful friend, for now you still have each other and the many shared memories. Hugs from me.
I went through this when my corgi, Buffy, died unexpectedly. I was crushed and ended up getting Izzy 3 days later (not by design, the perfect puppy just happened to be available). Sparty took about 6 months to warm up to Izzy. Looking back on it, I probably moved too fast for him. Mostly he just needed attention from me and he adjusted fine in time. I think you just need to let yourself and Annie grieve and spend time with each other. There is probably no right way to do this.