My name is ***** ***** I’ve been involved professionally with dogs in the health and behavioral fields for over 18 years. It will be my pleasure to work with you today.
I'm so sorry to hear of your loss. Dogs grieve much like people do. In addition, she also picks up on the emotions of those around her and I'm sure that you are still grieving over her litter mates death. I know how you feel exactly as I watched 3 of my dogs search for a dog of ours that had died. They also were depressed and subdued for days before they snapped out of it and they still had each other.
You can help your dog and yourself by going places new like a park or pet store where your dog can be stimulated. Spend extra play time with your dog as their play buddy and companion is gone and not only does your dog not know what's going on, but your dog senses your feelings as well.
Your dog will adjust with your help; it will just take a little while, like it will for you. The new pup will help. Her behavior is perfectly normal for an adult female dog and a puppy. See adult dogs have to teach puppies how to act around adult dogs. Their mom's start this training when they are young but pups are given a lot of leeway and as they get older, adult dogs will start reprimanding them for unsuitable behavior. They will let them get away with some things, but they will reprimand them with growls and even nips if he gets too bouncy near her or tries to jump on her.
Pups love to play but they often are too rambunctious and bite too hard. Adult dogs do not just run up on each other. They approach and the other dog either warns them off or displays body language letting them know it is ok to approach. So your female is not acting inappropriately as long as she isn't drawing blood. Let them sort it out. It will take her a little while for her to adjust to the loss but if you treat her relatively normally she should adjust and accept the pup easier as the pup matures.
As you mentioned, your heart is breaking and she picks up on your feelings. Also try not to pay more attention to the pup than her. It was her home first, so feed her first, give her attention first and treats first even if you need to block the puppy to give her the attention first. It will also help the pup learn that she is the boss in the house. That may change when he matures into a full adult but when he is a pup, she is the boss.
Since I know you are hurting, perhaps you will find this website helpful.
I hope this information is helpful to you. If you would like any additional information or have more questions please don’t hesitate to press the reply to expert or continue conversation button so I can address any issues you still have . If you do find this helpful, please take this opportunity to rate my answer positively so I am compensated for my time.