My young dog has been anxious and aggressive to outsiders since our old dog has passed away. Do you have any suggestions?

I always suggest having a thorough veterinary exam and bloodwork with any personality/temperament change. It may be that she's anxious now that she doesn't have the older dog to rely on for comfort and structure. I know that some of my dogs are very upset when we lose a member of the family (canine or human).

If everything checks out ok medically may be you should look into some type of calming supplement, like a CBD product. Something that can be given for anxiety but that doesn't actually sedate or alter the dog, just rebalances them physically and mentally. It might also be a good idea to do some structured training sessions each day to get her mind working. Mental exercise and having structured activity is helpful for anxiety and emotional healing.